Overhaul to build.gradle

- Updated README.md
- Gradle now builds javadocs and sources jar file
- It now shouldn't derp when importing and attempting to run it from
  Eclipse

Note: I HIGHLY recommend deleting your .gradle folder in your user
directory and recloning this project and setting it up again as recent
changes to ForgeGradle caused my cloned copy to not play nicely. If you
still have issues then feel free to contact Grinch on #spoutcraft
(irc.esper.et)

Signed-off-by: Steven Downer <grinch@outlook.com>