Nexage Plugin 

Featetures:
- Add OpenRTB generic plugin
- Fix: Now generating random auction ids (not sequencial)
- Fix: Rubicon exchange now correctly parse the adm tag (tag-parsing module was added)
- Add specific config for the OpenRTB plugin for Mopub and Nexage.
- Added templates of body request for Mopub and Nexage.
- Add some tests (now only for the tag_parsing module)