Don't use deprecated function.
Fix signed/unsigned warnings.
Switch from google-test to google-mock.
Merge branch 'master' into super_duper

Conflicts:
	cpp/util/json_wrapper.h
Update LogLookup<> through a callback on Database<>.
Add util::Status
comments
Merge pull request #191 from AlCutter/status

Add util::Status and util::StatusOr