get avatar api changes running in fxa-dev instances

Not heavily tested, but this will store an image that can be retrieved from the URL returned.

```
$ curl -k -D - -X POST -H "Content-Type: image/jpeg" -H "Authorization: Bearer f95c865fea024fb232fedbfd4fdf94d41b5825d71442813f4dd961889aec97d3" --data-binary @mapleleafs.jpg "https://jrgm7.dev.lcip.org/profile/v1/avatar/upload"
HTTP/1.1 100 Continue

HTTP/1.1 201 Created
access-control-allow-headers: Authorization, Content-Type, If-None-Match
access-control-allow-methods: GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS
access-control-allow-origin: *
access-control-expose-headers: WWW-Authenticate, Server-Authorization
access-control-max-age: 86400
cache-control: no-cache
Content-Type: application/json; charset=utf-8
Date: Sun, 07 Sep 2014 21:23:11 GMT
Server: nginx/1.4.7
Content-Length: 79
Connection: keep-alive

{"url":"https://jrgm7.dev.lcip.org/profile/a/2c003724924899abdc632695fd9b5347"}
```