Members feature

Adds ability for websites to have members

![img](http://cl.ly/image/153f1j1I3Q3R/Screen%20Shot%202014-10-24%20at%2014.03.05.png)

![img](http://cl.ly/image/2C3X3q2o0e0r/Screen%20Shot%202014-10-24%20at%2013.54.55.png)

![img](http://cl.ly/image/0x3I350L2b3d/Screen%20Shot%202014-10-24%20at%2014.09.13.png)

![img](http://cl.ly/image/0J1Q1a1Q2v2R/Screen%20Shot%202014-10-24%20at%2014.07.12.png)

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Things left to do
- [ ] Password reset feature for members
- [ ] Add default templates for this so that new websites get them default
- [ ] Documentation about how to use this feature
- [ ] Allow admin to disable signups