enable file extension based content negotiation
Merge pull request #150 from autermann/uri-content-negotiation

Enable file extension based content negotiation
Merge pull request #14 from enviroCar/dev

Dev
bug in validation. we do not produce any output at all.
remove "obdDevice" from JSON encoding. closes #152
allow three more properties in track.json. closes #153
Merge pull request #154 from matthesrieke/dev

fix issues #152 and #153
debugging statements, related to #155
Merge pull request #156 from matthesrieke/dev

debugging statements, related to #155
Merge pull request #157 from enviroCar/dev

merge recent bugfixes
add methods for pending friend requests.
set up paths in FriendsResource to get list of pending friend requests
add mongo methods to identify non-bidirectional friendships
add Resource method to decline a friend request.
remove friends bi-directional as invoked by an explicit request
Merge pull request #164 from matthesrieke/feature-pending-friend-requests

Feature pending friend requests
expose Link header with Access-Control-Expose-Headers
Merge pull request #166 from autermann/cors-link

Expose Link header with Access-Control-Expose-Headers
Merge pull request #167 from enviroCar/dev

merge recent developments
Fix endpoints in README.md