Support beta xcode

Changed check to look for the directory in library, as opposed to the
com.apple receipt as there appears not to be one with the beta Xcode
6.0.
Added rvm support.

Support rum based installs of 1.9.3. Couldn’t get the brew version to
install correctly on Yosemite so used rvm, which worked swimmingly.
Merge branch 'beta-xcode'
Merge branch 'rvm-support'