Relationships

1) add view RelationshipsController specs
2) add Relationship model, specs
3) add validation on relationship to be unique
4) add user socializes spec - following, unfollowing

Please, approve.
![animated-light-bulb-image-0002](https://cloud.githubusercontent.com/assets/7385469/5429422/12c23a3c-83eb-11e4-9785-a39a309b861f.gif) lol thank you :)