Gradle changes

Currently this will replace the version number in the source code as well as the mcmod.info.

Experimented with adding a -Pdev argument to the build task, which would add "-DEV" to the end of the jar file, had issues with not properly replacing in the java source.
For now I'm not going to play around more with ForgeGradle, I've spent about 3 hours making it work, or trying to.

If anyone wants to help me out with the other two features as specified in #35, be my guest.