Updated README.md

Long overdue, but I finally got around to redoing my fork :3

-Removed spaces between links
-Removed some now-useless stuff, and added a generalization (the
IMPORTANT part)
-Updated Java version
-Clarified Github for Windows/Mac part
-Updated for pahimar's build.xml change (ant build)
-Updated for Repository Next
(https://github.com/blog/1529-repository-next)