Connector should recognize local transfers

[emschwartz]

If you request a quote from a connector from one account to another on the same ledger, right now the connector won't recognize that there is a direct path and it will give you a path from ledger A -> B -> A instead. The connector should (take pity on you and) return a simple transfer object with no nested transfers (and probably no fee)

[sentientwaffle]

This will be fixed by #150