Update README.md

point to release branch build badge
TISTUD-6548 Studio installer version on Mac displays 3.0 despite being 3.3.0
  - Inject versions and year into Info.plist as part of our build rather than relying on updating it ourselves
  - Fix the update site we point at to Kelper from Indigo (since we now build on 4.3 as our base).

Conflicts:
	builders/com.aptana.rcp.build/build_local.properties