BLD: Adds versioneer

versioneer let's us track the version using git tags. This prevents
issues like the 0.8.2->0.8.3 push. This also puts the number of commits
from the release and the commit you are on in the version.

setup.cfg

@@ -5,4 +5,15 @@ with-ignore-docstrings=1
 with-timer=1
 
 [metadata]
-description-file = README.md
+description-file = README.rst
+
+# See the docstring in versioneer.py for instructions. Note that you must
+# re-run 'versioneer.py setup' after changing this section, and commit the
+# resulting files.
+[versioneer]
+VCS=git
+style=pep440
+versionfile_source=zipline/_version.py
+versionfile_build=zipline/_version.py
+tag_prefix=
+parentdir_prefix= zipline-