Port Metasploit::Yard::Aruba

MSP-11400

Port the working rvm gemset and project gem installation step definitions and supporting API from rapid7/metasploit-yard to our fork of aruba so that the step definitions can be used in both rapid7/metasploit-yard and rapid7/metasploit-version and any future project that needs to test installations in isolated gemsets in cucumber features.

# Verification Steps

## Rubocop
- [ ] `rake rubocop`
- [ ] VERIFY no offenses

## Specs
- [ ] `rake spec`
- [ ] VERIFY no failures

## Cucumber

### JRuby
- [ ] `rvm use jruby@aruba`
- [ ] `rm Gemfile.lock`
- [ ] `bundle install`
- [ ] `rake cucumber cucumber_wip`
- [ ] VERIFY no failures

### MRI
- [ ] `rvm use ruby-1.9.3@aruba`
- [ ] `rm Gemfile.lock`
- [ ] `bundle install`
- [ ] `rake cucumber cucumber_wip`
- [ ] VERIFY no failures

**NOTE: @shuckins-r7 and I have different `rvm env` formats, but we don't know why, so if cucumber fails, you may have a third format that we need to support**