Implented integration to Google Closure compiler for better js code minification

[rilmay]

I noticed that the current js code minifier is simple whitespace/newline stripper. Google's compiler is a proven and configurable minification tool that can significantly reduce the amount of code, and I thought it would be a good idea to use it in a project. In PR, I have not set this minifier as a standard one, but it will be cool that users will be able to set it in the configuration.

[tipsy]

I think the core of j2html should be dependency free, so I would provide the option to configure your own minifier (through an interface), and provide this as a separate artifact instead.