Adds argument to opt out of class insertion

The `--no-class-insertion` flag will disable the insertion of the
redscript inheritence code. This is usefull if you're using someone
elses `extend` method for inheritence (backbone, ember, etc).
Classical Inheritance method insertion

This commit will enable the insertion of the Resig simple inheritance
code. See http://ejohn.org/blog/simple-javascript-inheritance/ for more
info on how the inheritance works.

If the `--no-class-insertion` is passed, this code will not be inserted.
ignores global vars