Use setuptools if possible, add development docs

- If setuptools is available, use that.
  Setuptools can be very handy in development, because it provides
 `python setup.py develop`.
- Add development documentation, explaining how to use setuptools'
  develop with a virtual environment to work on cheat.
- Backwards compatibility with distutils is maintained.
  If setuptools is not available, distutils will be used.

.gitignore

@@ -3,3 +3,4 @@ MANIFEST
 build
 cheat.egg-info
 dist
+venv

README.md

@@ -117,6 +117,27 @@ enable this feature, set a `CHEATCOLORS` environment variable:
 export CHEATCOLORS=true
 ```
 
+Development
+-----------
+
+Virtual environments and `setuptools` can be used to develop `cheat`:
+
+Create a virtual environment with [virtualenv](http://docs.python-guide.org/en/latest/dev/virtualenvs/):
+
+    $ virtualenv venv
+
+Activate it:
+
+    $ source venv/bin/activate
+
+Install `cheat` in the venv in [development mode](http://setuptools.readthedocs.io/en/latest/setuptools.html#development-mode):
+
+    $ python setup.py develop
+
+Now `cheat` can be run from inside the venv:
+
+    $ venv/bin/cheat
+
 See Also:
 ---------
 - [Enabling Command-line Autocompletion][autocompletion]

setup.py

@@ -1,4 +1,7 @@
-from distutils.core import setup
+try:
+    from setuptools import setup
+except ImportError:
+    from distutils.core import setup
 import os
 
 setup(