Fix syntax error in Python 3.3.

“Unicode Raw” strings are no longer supported in Python 3.3, and cause a syntax error. See http://bugs.python.org/issue15096. Without this fix, Pystache gives a syntax error when used in a Python 3.3 environment.
Fix another Python 3.3 syntax error.
Avoid using the "ur" string prefix.

This commit is more a matter of style since the Python 3 code generated
by 2to3 is valid under Python 3.3.  This merges remote-tracking branch
'sentience/development' into development and closes issue #152.