Updated README to reflect recent move to sbt 0.13.0
The project's build is now based on sbt 0.13.0. Hence, it was time to update
the rather outdated Eclipse and Build section in the README.
Bumped mima version to 0.1.4
Updated instructions for using sbteclipse
updated link to issue tracker in README
* Added link to the Mailing list.
* Removed paragraph about Eclipse launch configurator (because the file has been deleted already)
Updated README with sbteclipse information.