Node improvements (#47)

* block partial persist

* replaced refactored files with old one.

* removed gokit/log from deps

* Tweaks to not overburden remote nodes with getheaders/getblocks

* Changed Transporter interface to not take the server as argument due to a cause of race warning from the compiler

* started server test suite

* more test + return errors from message handlers

* removed --race from build

* Little improvements.

pkg/core/blockchainer.go

@@ -0,0 +1,17 @@
+package core
+
+import "github.com/CityOfZion/neo-go/pkg/util"
+
+// Blockchainer is an interface that abstract the implementation
+// of the blockchain.
+type Blockchainer interface {
+	AddHeaders(...*Header) error
+	AddBlock(*Block) error
+	BlockHeight() uint32
+	HeaderHeight() uint32
+	GetHeaderHash(int) util.Uint256
+	CurrentHeaderHash() util.Uint256
+	CurrentBlockHash() util.Uint256
+	HasBlock(util.Uint256) bool
+	HasTransaction(util.Uint256) bool
+}