CI: Attempt to use rvm-installed Bundler, RubyGems (#207)
CI: Attempt to use rvm-installed Bundler, RubyGems (#207)

This is an attempt to make the CI configuration smaller, more confident. I am guessing that we are not relying on Bundler 1.x-specific behavior, so this commit is a try-out of that.
discourse/mini_racer,seanmakesgames/mini_racer,discourse/mini_racer,seanmakesgames/mini_racer,discourse/mini_racer,discourse/mini_racer,seanmakesgames/mini_racer,seanmakesgames/mini_racer,seanmakesgames/mini_racer