Allow users to change their avatar

#### Need
```gherkin
In order to have people view my avatar
As a user
I want to change my avatar
```

#### Deliverables
- [ ] A way for users to set / change their avatar

#### Prerequisites
- Gravatar
- profile_set.html
- using gravatar from templatetags (see profile.html)

#### Solution
Add a link to profile_set.html that redirects to gravatar (simmilar to github)