review post: Merge into the parent branch

From now on, while in the parent branch mode, the current branch is
merged into the parent branch unless -no_merge is specified.

Also, -merge_no_ff can be specified to use git merge --no-ff.

Change-Id: 568cae4930
Story-Id: SF-42
review post: Add -push_parent flag

When this flag is specified, the parent branch is pushed after the
review requests are posted, but only if merge occured.

Change-Id: 6f95aef3dd
Story-Id: SF-42