Update Readme.rst

Corrected 'a almost' to 'an almost'

Author: iepathos

Readme.rst

@@ -23,6 +23,6 @@ Topics include:
 - How to interface w/ hg from git easily
 - what libraries to use for what
 
-If you are not fond of reading reStructuredText, there is a
+If you are not fond of reading reStructuredText, there is an
 almost up-to-date `HTML version at docs.python-guide.org
 <http://docs.python-guide.org>`_.