This enables easier testing of feedstock fixes.
Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1826 from cpcloud/test-windows-ci-build and squashes the following commits:

4dbf284 [Phillip Cloud] SUPP: Allow passing a branch to ci/feedstock.py

Fixes #1786     This is in an extremely early state, but I wanted to
open this for comment now as I'm not likely to get the chance to work
much on it for a few days.
Author: Ian Rose <ian.r.rose@gmail.com>

Closes #1787 from ian-r-rose/postgis and squashes the following commits:

db50529 [Ian Rose] Ensure that empty resulting dataframes work okay.
90673fc [Ian Rose] Add ST_DWithin and ST_DFullyWithin.
38aa985 [Ian Rose] Use importorskip for geopandas in test suite.
10a10fc [Ian Rose] Only load geospatial data into postgis when python >= 3.6.
0a5daca [Ian Rose] Add postgis marker to setup.cfg
4156bba [Ian Rose] Don't support postgis on python 3.5
60d0cb4 [Ian Rose] Move PostGIS test functions into separate file.
e02aa72 [Ian Rose] Use more explicit name for geo-supported.
a7f6566 [Ian Rose] Make a copy of sqlalchemy table list since it returns a mutable reference to its own list.
00a8a40 [Ian Rose] Add x,y commands.
30a6d55 [Ian Rose] Add intersection and difference tests.
51b9c34 [Ian Rose] More PostGIS tests.
112f097 [Ian Rose] More fussing with gdal reqs on python 3.5
7862b33 [Ian Rose] Don't run postgis functions on Windows -- PostGIS version on chocolatey seems pretty out-of-date.
b547dd1 [Ian Rose] Add some more PostGIS tests.
3c25c8e [Ian Rose] Pin pyproj on python 3.5
b231287 [Ian Rose] Skip failing test for now.
8f7dabe [Ian Rose] Add area test.
e42d174 [Ian Rose] Add tests for selecting geospatial columns.
919a876 [Ian Rose] Begin with PostGIS testing.
a1c0927 [Ian Rose] Load geo sample data into postgres db when testing.
f68ae19 [Ian Rose] Add deps to CI
485c90c [Ian Rose] Add WKT, WKB casting functions.
703381f [Ian Rose] Add optional requirements for geospatial to setup.py
85b5766 [Ian Rose] Add some missing geo value methods.
319ce4e [Ian Rose] Lint.
98457f8 [Ian Rose] More geospatial ops.
2429781 [Ian Rose] Fix up buffer.
960066e [Ian Rose] More work on adding extra geo functions.
eb59626 [Ian Rose] Work on adding a bunch of new GeoOperations.
ab509a9 [Ian Rose] Handle geography vs geometry types.
c4d2f38 [Ian Rose] Convert to geodataframe if geometry column is found.
bf22bbf [Ian Rose] Don't make geoalchemy2 and geopandas required.
1750a58 [Ian Rose] Initial work adding geoalchemy2 functions.

Support row-based trailing windows bound by a maximum look-back period
Author: Emily Reff <emily.reff@twosigma.com>

Closes #1825 from emilyreff7/maxrows and squashes the following commits:

7fae189 [Emily Reff] add docstring and other minor changes
c14660d [Emily Reff] use namedtuple instead of dict for rows with max lookback
be7e050 [Emily Reff] Accept rows-with-max-lookback as preceding parameter

See issue: #1832
Author: Emily Reff <emily.reff@twosigma.com>

Closes #1838 from emilyreff7/timedelta and squashes the following commits:

ee78f11 [Emily Reff] Adding timedelta to error message
fbf85b6 [Emily Reff] allow pandas timedelta in rows_with_max_lookback

Closes #1839
Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1840 from cpcloud/tighten-pytest-version and squashes the following commits:

2c883b2 [Phillip Cloud] SUPP: Tighten pytest version

This caused a few failures with downstream code, so I've reverted the
changes to ibis/pandas/core.py.  I've left other fixes from #1758
unchanged.  I'll revisit the reimplementation in the near future.
Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1837 from cpcloud/revert-topo and squashes the following commits:

c9662ac [Phillip Cloud] Just pass kwargs through
5d8ec82 [Phillip Cloud] Make zero argument UDFs work again
9fa4481 [Phillip Cloud] Revert toposort change
d9c00ef [Phillip Cloud] Remove unnecessary code
deed6aa [Phillip Cloud] Revert select parts

Closes #1842
Author: Emily Reff <emily.reff@twosigma.com>

Closes #1843 from emilyreff7/maxrows-fix and squashes the following commits:

55646c2 [Emily Reff] add tests for replace and fix equals fn
3222850 [Emily Reff] Merge branch 'master' of https://github.com/ibis-project/ibis into maxrows-fix
6c04905 [Emily Reff] add max_lookback to window replace and combine functions
ee78f11 [Emily Reff] Adding timedelta to error message
fbf85b6 [Emily Reff] allow pandas timedelta in rows_with_max_lookback

…be implemented

Closes #1833
Author: Emily Reff <emily.reff@twosigma.com>

Closes #1844 from emilyreff7/exceptions and squashes the following commits:

782b21b [Emily Reff] fix test structure and error messages
77891bc [Emily Reff] Merge branch 'master' of https://github.com/ibis-project/ibis into exceptions
f95c8a9 [Emily Reff] Merge remote-tracking branch 'origin/maxrows-fix' into exceptions
890e270 [Emily Reff] Raise exception on backends where rows_with_max_lookback can't be implemented
55646c2 [Emily Reff] add tests for replace and fix equals fn
3222850 [Emily Reff] Merge branch 'master' of https://github.com/ibis-project/ibis into maxrows-fix
6c04905 [Emily Reff] add max_lookback to window replace and combine functions
ee78f11 [Emily Reff] Adding timedelta to error message
fbf85b6 [Emily Reff] allow pandas timedelta in rows_with_max_lookback

Example run:    ```  $ dev/genrelease.py 1.2.0  * :release:`1.2.0
2019-06-19`  * 🐛`1842 major` Add max_lookback to window replace
and combine functions  * 🐛`1837 major` Partially revert #1758  *
:support:`1839` Tighter version spec for pytest  * :support:`1838`
allow pandas timedelta in rows_with_max_lookback  * :support:`1825`
Accept rows-with-max-lookback as preceding parameter  *
:support:`1786` PostGIS support  * :support:`1826` Allow passing a
branch to ci/feedstock.py  ```
Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1845 from cpcloud/release-note-generator and squashes the following commits:

4e7eae1 [Phillip Cloud] Add rls/release to roles
f260477 [Phillip Cloud] SUPP: Generate release notes from commits

Closes #1849
Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1850 from cpcloud/fix-empty-schema-repr and squashes the following commits:

559187b [Phillip Cloud] BUG: Fix repr of empty schema

Closes #1841
Author: Emily Reff <emily.reff@twosigma.com>

Closes #1848 from emilyreff7/orderby and squashes the following commits:

c75f37b [Emily Reff] fix error msg
b520a8f [Emily Reff] fix error message and line alignment
d1cbe2e [Emily Reff] validate order_by when using rows_with_max_lookback window

Closes #1823
Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1851 from cpcloud/fix-nested-array-repr and squashes the following commits:

1cfa2a4 [Phillip Cloud] BUG: Fix nested array literal repr

Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1855 from cpcloud/bug-fix-psql-call and squashes the following commits:

7029c4a [Phillip Cloud] BUG: Fix call to psql causing failing CI

Also did some refactoring of `backends.py`.  Closes #1846
Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1847 from cpcloud/sa-skip-backend-all-tests and squashes the following commits:

64b6dca [Phillip Cloud] BUG: Use the right value for testing the sql attribute in test_sql test
d3831d2 [Phillip Cloud] BUG: Properly skip when missing dependencies on backend-all tests

Add 2 new geo spatial functions to OmniSciDB backend:    - set_srid  -
transform    Add a cast to geographic type
Author: Ivan Ogasawara <ivan.ogasawara@gmail.com>

Closes #1836 from xmnlab/add-more-geo-funcs-mapd and squashes the following commits:

9eaf660 [Ivan Ogasawara] Added new geo functions to omniscidb backend

Author: Phillip Cloud <cpcloud@gmail.com>

Closes #1857 from cpcloud/rls-1.2.0 and squashes the following commits:

b5f349e [Phillip Cloud] RLS: 1.2.0