Chen share trip

User can share and unshare a trip

![user can share and unshare a trip](https://cloud.githubusercontent.com/assets/3759510/5185571/631e0be4-748e-11e4-9c78-7b2e5071f6dd.gif)

would this really be an index?  Or would it be a show?  It seems like you're showing data from one trip group