Request membership

Details to follow. Here are some snapshots:

#### The request membership button (note not a logged in user):
![selection_020](https://f.cloud.github.com/assets/2665886/713699/9c0395b2-ded7-11e2-8ed8-877a513eb675.png)

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####  The form (user not logged in):
![selection_021](https://f.cloud.github.com/assets/2665886/713701/b2b7cb8e-ded7-11e2-9a91-9e028df32156.png)

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####  The form (user logged in):
![selection_022](https://f.cloud.github.com/assets/2665886/713702/bca1d6da-ded7-11e2-8d33-10887f719a3d.png)

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#### The coordinator view for responding to membership requests
![selection_023](https://f.cloud.github.com/assets/2665886/713913/d0307b5e-dee4-11e2-9678-d40d59e7d087.png)