feature finish: Add links into commit message

This patch makes feature finish insert the links of the Review Board
review request and the Pivotal Tracker story connected with the feature
into the merge commit message before pushing to origin.

Change-Id: I30a1453651a0deb66dfa84b012329437dd9a614e
Signed-off-by: Ondrej Kupka <ondra.cap@gmail.com>