DiffFormatterTest: Add a test to confirm the default rename detection settings

DiffFormatterTest: Add a test to confirm the default rename detection settings

Add a test that confirms:

- No rename detector is initialized by default

- Rename detector is initialized after calling setDetectRenames(true)

- Rename limit and rename score have the default values 400 and
  60, respectively. Note that there are no constants for these values
  so the test hard codes them.

Change-Id: I327e2b348a40ef67d8a184e5ab09f4e9ab573e1c
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>