Change accept button label according to the selection

The current label "Approve" is very confusing, at least if user is about to reject the offer.

This PR changes the text to "Accept" and "Decline" according to the selection

![screen shot 2014-12-08 at 10 52 34](https://cloud.githubusercontent.com/assets/429876/5337136/b6c82542-7ecd-11e4-89d5-20746d61f193.png)