Password reset

This is ready for review (@jh-bate or @ianjorgensen?). Password reset (request from link on login screen, as well as confirm from link in email), working with mock API.

For integration with real API, all I'm missing is:

**1) Update platform client**

Two calls (see `mock/api/user` for more info):

```javascript
tidepool.requestPasswordReset(email, function(err) { /*...*/});

tidepool.confirmPasswordReset(payload, function(err) { /*...*/});

// where `payload` looks like:

payload = {
  key: 'def801',
  email: 'mary.smith@example.com',
  password: 'test123'
};
```

**2) Email templates**

All I need is for the email to have a link that points to:

```
http://blip.tidepool.io/#/confirm-password-reset?key=def801
```

@jh-bate, I was planning to get to `platform-client` (1) tomorrow, but if you have the time and want to take care of it, you are welcome to :) If you're already busy, I'll do it, no problem. Thanks!
Yup, good suggestion from @HowardLook. We can change it to something like 3 characters in devel if we want. It defaults to 8.