Add timing of generic tags (SimpleNode and InclusionNode)

This is done by patching the generic_tag_compiler and keeping track
of all the nodes passing this function. We can't simply patch them
like the BlockNodes because the node class is generated separately for
each tag.

Bit ugly hack but it works pretty well :-)
Merge pull request #19 from mvantellingen/generic-tags

Add timing of generic tags (SimpleNode and InclusionNode)