The rbt land command now supports options for dealing with review

requests with commit history. When using history (and not squashing via

LAND_SQUASH/--squash), the review request will be applied via

rbt patch using history. These patches will be applied to the current

branch and merged into the destination branch, as if it were a local

change.

Ran unit tests.
Landed review requests using the following combinations of flags:

 - --squash;

 - --no-squash --squash-history; and

 - --no-squash --with-history.

The review requests landed correctly.