expose tx-report tempids in a proxy Map object (fixes #22)

TxReport.tempidMap gives a limited Map[DId, Long] interface over the tempids returned by a transaction
the implicit arguments for resolve are unneeded, we simply use the db value returned by the transaction
Merge pull request #30 from pellucidanalytics/topic/txreport-tempidMap

expose tx-report tempids in a proxy Map object (fixes #22)