Add actions for photos with tags from the Instagram realtime api.

1. Adds a User subscription via the Instagram API when a user connects to their instagram account.
2. StreetCred api responds to the Instagram negotiation callback check via a GET route on /api/actions/instagram
3. User posts a photo to instagram with a tag that matches a StreetCred action type.
4. Instagram sends a POST to StreetCred with the user id of the new photo
5. StreetCred checks the photo's tags against the Instagram ActionTypes
6. If it matches then StreetCred gives the user credit for the Action