Ledger integration (#931)

Merges the keybase and Ledger code from go-crypto (which is no more) into the SDK
Adds support for Ledger into gaiacli
Cherry-picks updated error handling from #1158

examples/democoin/cmd/democoind/main.go

@@ -6,7 +6,7 @@ import (
 
 	"github.com/spf13/cobra"
 
-	abci "github.com/tendermint/abci/types"
+	abci "github.com/tendermint/tendermint/abci/types"
 	tmtypes "github.com/tendermint/tendermint/types"
 	"github.com/tendermint/tmlibs/cli"
 	dbm "github.com/tendermint/tmlibs/db"