mGerrit: Almost completely fix viewing of CyanogenMod's gerrit

CyanogenMods gerrit is almost completely supported
the diff view is not supported. The API's are not available
in their version :(

bump version to v2.03.04

Patch Set 2: remove DiffDialog and show exception dialog
             if the call for a DiffView fails. This returns
             null from volley if we can't get the diff.

Change-Id: I93fc5077dfcbe3ff3578688fbade7118b4fcf446