Added nodes for recursive decent parser

Created a Group, text and python node.
Implemented eval expression for parser

Code now parses text and python expressions. also minor bug fixes.
Added wrapper

Added the expand wrapper to the parser.
Implemented include tag

Implemented the include tag for the template engine.
Fixed parse_group function

Function now uses recursion rather than incrementation.
DocStrings and Doctest implemented :)

Yeah, we pretty much did that.
Created if node and modified template

Todo: create group until end if
Merge branch 'template-engine'