Allow client to inject own Mustache.Compiler

I've removed the injection of nullValue and emptyStringIsFalse properties into MustacheViewResolver and, instead, replaced them with the ability for the client to optionally inject a pre-customized compiler. This commit is still backwards compatible with versions 1.1.1 and prior since the Compiler injection is optional. There is an incompatibility with 1.1.2 since the nullValue and emptyStringIsFalse properties have been removed.

This gives the client the flexibility to try different Compiler configurations within their own code base. Also, this prevents this library from having to be updated every time a new Compiler property is added/removed from the Mustache library.