Parsing rcsdiff -u

Summary: Added some sample rcsdiffs for adding and deleting a line from a file. Wrote some test cases to be tested by ArcanistDiffParser.

Test Plan: By making all the test cases pass.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin, AnhNhan

Differential Revision: https://secure.phabricator.com/D5324