fixed JAVA problem.  JRE 7 doesn't work.  Updating the script to add JRE 6u45 support.  Added error checking

JRE 7 not supported by JRUBY.  Need JRE 6u45.

Needed better error checking.

Needed to move the JRE download later in the script so we don't confuse the user.

Added git-core install since we have the JRE 6u45 bin file in the github repo for simplicity.  We all love Oracle, but downloading from their site introduces a potential break point.