Fixes bug introduced in a previous merge when the CDTDatastore -conflictsForDocument
method was removed.

Adds -conflictsForDocumentId to CDTDatastore+Internals.
Modifies CloudantReplicationBase+CompareDb -compareDocIdsAndAllRevs:withDatabase
to call -conflictsForDocumentId.
Merge pull request #35 from cloudant/32009-fix-broken-replication-tests

Fixes bug introduced in a previous merge when the CDTDatastore -conflictsForDocument method was removed.