`echo yes | rvm implode` no longer works. Explicitly remove RVM. (cc @havenwood)
Ensure chruby-exec parameters are shell-quoted.

- Preserve quotes in chruby-exec command parameters (closes #283).
- Fixes a bug where RUBYOPT options passed to chruby-exec are ignored.
Merge pull request #285 from havenwood/chruby-exec-parameters

Ensure chruby-exec parameters are shell-quoted.
Match comments in setup.sh to what the script actually does.