Adding the ability to use --include-path option at the compilation #49

Hi.

Currently, we can set the --include-path option, like every options, before calling LessCompiler#init().

I would like to change it when I compile a file, without calling LessCompiler#init() again, because of its performances cost.

Actually what I really need is a new method like this:

public synchronized String compile(File input, String name, List<String> paths) throws LessException {
}

Thanks,

Guillaume