Call rvm by path for rvm_ruby install/uninstall/remove.

This will skip any automated installation of requirements.

References wayneeseguin/rvm#1466
Refereces wayneeseguin/rvm-gem#11
Long variable names are not good.
Code reformatting.
Require rvm gem >= 1.11.3.6 (support for :rvm_by_path).
Merge pull request #154 from fnichol/skip-requirements

Call rvm by path for rvm_ruby install/uninstall/remove.