Remove pubsub and replace w/ polling head of chain (#122)

* Rename geth package structs to not be prefaced with package name

* No longer need to dump schema since Travis uses migrate

* Rearrange history package

* Removed double request for receipt from block rewards

* Remove Listener + Observers and Replace w/ Polling Head

* Potential Short term Issue w/ Infura (ignore these tests for now)

pkg/core/blockchain.go

@@ -6,9 +6,6 @@ type Blockchain interface {
 	GetBlockByNumber(blockNumber int64) Block
 	LastBlock() *big.Int
 	Node() Node
-	SubscribeToBlocks(blocks chan Block)
-	StartListening()
-	StopListening()
 	GetAttributes(contract Contract) (ContractAttributes, error)
 	GetAttribute(contract Contract, attributeName string, blockNumber *big.Int) (interface{}, error)
 	GetLogs(contract Contract, startingBlockNumber *big.Int, endingBlockNumber *big.Int) ([]Log, error)

pkg/core/blockchain_observer.go

@@ -1,5 +0,0 @@
-package core
-
-type BlockchainObserver interface {
-	NotifyBlockAdded(Block)
-}