First approach to make tag parsing work.
Fix Python 2 and PyPy compat
Add IF condition parsing
Added support for AND and OR in IF condition
Added support for IF-ELSE-ENDIF
Added support for comment tags
Added intelligent parsing for tag arguments
Added support for "for-endfor" and "for-empty-endfor"
Added some tests to verify replacement of iterator variable in for loops
Fix for loop counter lookup on Python2
Moved context, filters, etc into global rendering context
Fixed setting loop variable
Reworked tests
Merge pull request #27 from Markush2010/lexer-rewrite

Rewrote the whole lexer and parser handling to support tags like "if" and "for"