Run bundler with gemfile in example rails app directory
Run bundler with gemfile in example rails app directory

Any ruby process that opens subshell and tries to use any `bundler` commands
will end up using the current bundler env.

So everytime I ran `bundle install` from witihin `Open3.capture3` it would use
the already exisiting bundler environment setup for the gem. So when I tried to
run any commands rails would not be installed the example rails dir.

This commit fixes the problem by using `Bundler.with_clean_env` for more info on
how this works, please refer to [1].

1.) http://bit.ly/1TblIKA

mrageh/slow_factory_formatter,mrageh/slow_factory_formatter,mrageh/slow_factory_formatter