Fixing RTD build

After removing the `-e .` from requirements-dev.in, RTD can't build
because trio-websocket isn't installed. I configured RTD to install
from setup.py and then requirements-dev.txt, but then it fails because
setup.py picks packages that conflict with requirements-dev.txt. So
I'm abandoning pip tools in this commit and just using a hand-written
requirements-dev.txt.

Makefile

@@ -2,8 +2,6 @@
 # product:
 .PHONY: docs
 
-export PYTHONPATH = .
-
 coverage:
 	coveralls -v
 

docs/contributing.rst

@@ -15,53 +15,14 @@ environment, and install the developer dependencies::
     $ cd trio-websocket
     $ python3 -m venv venv
     $ source venv/bin/activate
+    (venv) $ pip install -e .
     (venv) $ pip install -r requirements-dev.txt
 
 This example uses Python's built-in ``venv`` package, but you can of course use
 other virtual environment tools such as ``virtualenvwrapper``.
 
-The instructions above *do not install the ``trio-websocket`` package itself*.
-Instead, you should add the project directory to ``$PYTHONPATH``. For example,
-add ``export PYTHONPATH=$(dirname $VIRTUAL_ENV)`` to the end of your
-``venv/bin/activate`` script.
-
-Development Dependencies
-------------------------
-
-You may have noticed in the developer installation instructions that the project
-is installed from ``requirements-dev.txt`` and not from ``setup.py``. This
-requirements file contains extra dependencies only needed for development, such
-as PyTest, Sphinx, etc. The requirements file is generated from
-``requirements-dev.in`` using `pip-tools
-<https://pypi.org/project/pip-tools/>`__, which pins each dependency to an exact
-version. This helps developers make reproducible builds across all environments,
-including Travis CI.
-
-If you need to modify the library's dependencies or modify the dev dependencies,
-you will need to regenerate the requirements file::
-
-    $ pip-compile --output-file requirements-dev.txt setup.py requirements-dev.in
-
-The ``pip-compile`` tool can also upgrade packages, which may be useful if you
-want to update pinned versions without changing the declared dependencies in
-``setup.py`` or ``requirements-dev.in``. The following command upgrades only the
-named packages::
-
-    $ pip-compile -P package1 -P package2 requirements-dev.txt
-
-Or you can upgrade all packages::
-
-    $ pip-compile --upgrade requirements-dev.txt
-
-
-After making changes to dependencies, you should check in the file you changed
-(e.g. ``setup.py`` or ``requirements-dev.txt``) as well as the generated
-``requirements-dev.txt``.
-
-In the future, when you checkout new branches or update existing branches, you
-should use ``pip-sync`` to synchronize dependencies. This command will add,
-upgrade, and even *remove* packages in order to make your environment match the
-expected development environment.
+The ``requirements-dev.txt`` file contains extra dependencies only needed for
+development, such as PyTest, Sphinx, etc.
 
 Unit Tests
 ----------

requirements-dev.txt

@@ -1,63 +1,9 @@
-#
-# This file is autogenerated by pip-compile
-# To update, run:
-#
-#    pip-compile --output-file requirements-dev.txt setup.py requirements-dev.in
-#
-alabaster==0.7.12         # via sphinx
-asn1crypto==0.24.0        # via cryptography
-async-generator==1.10
-atomicwrites==1.2.1       # via pytest
-attrs==18.2.0             # via outcome, pytest, trio
-babel==2.6.0              # via sphinx
-bleach==3.0.2             # via readme-renderer
-certifi==2018.10.15       # via requests
-cffi==1.11.5              # via cryptography
-chardet==3.0.4            # via requests
-click==7.0                # via pip-tools
-coverage==4.5.1           # via coveralls, pytest-cov
-coveralls==1.5.1
-cryptography==2.3.1       # via trustme
-docopt==0.6.2             # via coveralls
-docutils==0.14            # via readme-renderer, sphinx
-h11==0.8.1                # via wsproto
-idna==2.7                 # via cryptography, requests, trio, trustme, yarl
-imagesize==1.1.0          # via sphinx
-ipaddress==1.0.22
-jinja2==2.10              # via sphinx
-markupsafe==1.1.0         # via jinja2
-more-itertools==4.3.0     # via pytest
-multidict==4.4.2          # via yarl
-outcome==1.0.0            # via trio
-packaging==18.0           # via sphinx
-pip-tools==3.1.0
-pkginfo==1.4.2            # via twine
-pluggy==0.8.0             # via pytest
-py==1.7.0                 # via pytest
-pycparser==2.19           # via cffi
-pygments==2.2.0           # via readme-renderer, sphinx
-pyparsing==2.3.0          # via packaging
-pytest-cov==2.6.0
-pytest-trio==0.5.1
-pytest==3.10.0
-pytz==2018.7              # via babel
-readme-renderer==24.0     # via twine
-requests-toolbelt==0.8.0  # via twine
-requests==2.20.1          # via coveralls, requests-toolbelt, sphinx, twine
-six==1.11.0               # via bleach, cryptography, more-itertools, packaging, pip-tools, pytest, readme-renderer, sphinx
-sniffio==1.0.0            # via trio
-snowballstemmer==1.2.1    # via sphinx
-sortedcontainers==2.0.5   # via trio
-sphinx-rtd-theme==0.4.2
-sphinx==1.8.1
-sphinxcontrib-trio==1.0.1
-sphinxcontrib-websupport==1.1.0  # via sphinx
-tqdm==4.28.1              # via twine
-trio==0.9.0
-trustme==0.4.0
-twine==1.12.1
-urllib3==1.24.1           # via requests
-webencodings==0.5.1       # via bleach
-wsaccel==0.6.2
-wsproto==0.12.0
-yarl==1.2.6
+coveralls
+pytest
+pytest-cov
+pytest-trio
+sphinx
+sphinxcontrib-trio
+sphinx_rtd_theme
+trustme
+twine