Proper player cards

Player cards can be created for any player (not just hard-coded to the premier league). Additionally, the stats are specific to the selected team and competition instead of being for that player generally. This also means that dates are no longer hard-coded for the stats since they use the selected competition's start date.

We've also tweaked the stats that are presented to make them a bit more interesting in some cases.

![player-card-pr](https://cloud.githubusercontent.com/assets/29761/2613882/b156769e-bbdd-11e3-9f85-3657327524f4.png)