more readable railtie / engine output

related to #4

example output:

```
[GemBench] We found a Rails::Railtie or Rails::Engine in the following files. However, it is possible that there are false positives, so you may want to verify that this is the case.

	activesupport v4.0.2:
		/Users/john/.rbenv/versions/2.1.0-preview1/lib/ruby/gems/2.1.0/gems/activesupport-3.1.12/lib/active_support/i18n_railtie.rb:146
	rack v1.5.2:
		/Users/john/.rbenv/versions/2.1.0-preview1/lib/ruby/gems/2.1.0/gems/rack-timeout-0.0.3/lib/rack-timeout.rb:227
	actionpack v4.0.2:
		/Users/john/.rbenv/versions/2.1.0-preview1/lib/ruby/gems/2.1.0/gems/actionpack-3.2.14/lib/action_controller/railtie.rb:248
	railties v4.0.2:
		/Users/john/.rbenv/versions/2.1.0-preview1/lib/ruby/gems/2.1.0/gems/railties-3.2.14/lib/rails/application/configuration.rb:245
	action_dispatch-gz_static v0.0.3:
		/Users/john/.rbenv/versions/2.1.0-preview1/lib/ruby/gems/2.1.0/gems/action_dispatch-gz_static-0.0.3/lib/action_dispatch/gz_railtie.rb:42
	actionmailer v4.0.2:
		/Users/john/.rbenv/versions/2.1.0-preview1/lib/ruby/gems/2.1.0/gems/actionmailer-3.2.14/lib/action_mailer/railtie.rb:133
	activemodel v4.0.2:
		/Users/john/.rbenv/versions/2.1.0-preview1/lib/ruby/gems/2.1.0/gems/activemodel-4.0.0/lib/active_model/railtie.rb:77
	activerecord v4.0.2:
```