* update transformer to able to recheck headers
* put cap on rechecking header
* integration test for recheck headers
* use enum for recheck headers param; make recheck cap configurable
* update integration tests with new test config
* update omni pkg with new recheck header column type
* update migration with new migration tool and final tweaks needed to accommodate changes in omni pkg
* Upgrade geth from 1.8.15 to 1.8.18
* Update vat_tune to use shared repository methods
* Query blockchain by block hash instead of block number range
* Remove hash validation from repositories
* Fix vow flog integration test
* Update README Travis build sticker
* Update constants formatting per go fmt
* Update EthPublicKeyParser.ParsePublicKey to use discv5.PubkeyID method
* Address PR comments
- Delete header on conflict to prompt data refresh (cascade deletes all
data associated with that block)
- Derive header hash from rpc payload rather than computing it from data
(prevents hash mismatch between blockchain and cache)
* Add log_index field to flip kick
* Add log index to flop kick
* Add repo tests for Cat.file
* Add log_index to vat_flux
* Add log_index to vat_slip
* Add log_index to vat_toll
* Add log_index to vat_tune
* Add test to repos for updating checked headers
