====== Useful gems ======

^ Gem       ^ Description                 ^ Notes                                                                                                  ^
| rbconfig  | Reflection on configuration | Builtin > 1.8.7, see http://rbjl.net/35-how-to-properly-check-for-your-ruby-interpreter-version-and-os |
| railroady | GraphViz bases Classgrapher | Recommended in CS169.2x |
| RedCloth  | Textile                     | Used in typo, CS169.2x  | 
| omniauth  | SSO OAuth etc               | Google, Twitter, Facebook... CS169.2x |