Basic functionality for LinkStats.
Working through the tests of the LinkStats branch.
LinkStats: Added dispatcher test to verify stats are computed correctly
LinkStats is ready for PR. Last comment changes in this patch.
Merge branch 'master' into LinkStats
Changed addDomainWithExcludeReason in LinkStats to avoid race condition.
Doc change to LinkStats.
Merge branch 'master' into LinkStats

Conflicts:
	cassandra/datastore.go
Merge pull request #100 from iParadigms/LinkStats

Link stats