1.2.0: Number and Boolean JS types.

* Tag errors fail silently now. Error messages are returned describing what went wrong - formatted as an html comment. Find errors by searching the page's source for 'JSInclude Error'.
* JavaScript Number and Boolean types are now supported. Tag arguments like ```branch=true``` will now appear in ```$jsi.branch``` as a Boolean instead of a String. Note that Python's ```True``` and ```False``` will appear in the ```$jsi``` object as strings because JavaScript uses lower-case Boolean values.