User dashboard shows all of user's matches

* Rename opponent in match model to defender
* Make method `matches` to call all user's matches
* Matches are sorted by match-time
* List of matches shows on dashboard
![tumblr_m45cnxcwgd1rwqv34o1_400](https://cloud.githubusercontent.com/assets/755201/5305622/43b4227c-7bcb-11e4-9f4d-113be0b1333a.gif)