Stop copying all the files to war files. Proposed fix for issue 156.

When running warble command includes and excludes are ignored.
I think it might be because of a change that was done previously.
https://github.com/jruby/warbler/commit/79f830fcd335fc17dabab4d6f5821cb8c40f1ade#L2L35

With this change applied, I can now get only the files inside the war file that I want.