[WIP] Join team error #391

**This PR is waiting for feature specs to be added**

[Fix for Error when attempting to join a team instead of create a team #391] (https://assembly.com/coderwall/bounties/391)

The fix was a one liner - incorrect format of params, which caused `params.permit` to raise a 400 error.

I covered the related logic with specs and also did a little refactoring to make it easier to test and to understand the logic.  

Changes:

- extracted `#with_similar_names` to Team model method
- added shared notification bar that can be used to display flash error/notice from within js responses.
- added notification on success/failure of team creation

![screen](https://cloud.githubusercontent.com/assets/5670940/4705432/cdd92fec-587b-11e4-96dd-bd88627376dc.png)