clean up installation docs

docs/source/installation.rst

@@ -7,15 +7,24 @@ Alot depends on recent versions of notmuch and urwid. Note that due to restricti
 on argparse and subprocess, you need to run *`3.0` > python ≥ `2.7`* (see :ref:`faq <faq_7>`).
 A full list of dependencies is below:
 
-* `libmagic and python bindings <http://darwinsys.com/file/>`_, ≥ `5.04`:
-* `configobj <http://www.voidspace.org.uk/python/configobj.html>`_, ≥ `4.7.0`:
+* `libmagic and python bindings <http://darwinsys.com/file/>`_, ≥ `5.04`
+* `configobj <http://www.voidspace.org.uk/python/configobj.html>`_, ≥ `4.7.0`
 * `twisted <http://twistedmatrix.com/trac/>`_, ≥ `10.2.0`:
-* `libnotmuch <http://notmuchmail.org/>`_ and it's python bindings, ≥ `0.13`.
+* `libnotmuch <http://notmuchmail.org/>`_ and it's python bindings, ≥ `0.13`
 * `urwid <http://excess.org/urwid/>`_ toolkit, ≥ `1.1.0`
-* `urwidtrees <https://github.com/pazz/urwidtrees>`_,
+* `urwidtrees <https://github.com/pazz/urwidtrees>`_, ≥ `1.0`
 * `PyGPGME <https://launchpad.net/pygpgme>`_ ≥ `0.2`
 
-On debian/ubuntu these are packaged as::
+.. note:: urwidtrees was only recently detached from alot and is not widely
+          available as a separate package. You can install it e.g., via
+          `pip <https://pypi.python.org/pypi/pip>`_ directly from github:
+
+          .. code-block:: sh
+
+            pip install --user https://github.com/pazz/urwidtrees/archive/master.zip
+
+
+On debian/ubuntu the rest are packaged as::
 
   python-setuptools python-magic python-configobj python-twisted python-notmuch python-urwid python-gpgme
 
@@ -37,10 +46,6 @@ You can use `pip` to install directly from GitHub::
 
   $ pip install --user https://github.com/pazz/alot/archive/master.zip
 
-Or check out a more recent version, e.g. the master branch::
-
-  $ pip install --user https://github.com/pazz/alot/archive/master.zip
-
 Don't have pip installed? Just download and extract, then run::
 
   python setup.py install --user