Fixed up GetRawTransaction and updated GetBlock to handle verbose

Updated handleGetRawTransaction to populate all the fields required to
match bitcoind.  It still doesn't handle MULTISIG addresses correctly.

Changed handleGetBlock to implement new optional verbose (default true)
flag and also added a verboseTx flag to return TxRawDefault instead of
Txid.  When verbose=false, GetBlock returns hex-encoded wire bytes for
the block.
Fix handleGetBlock/handleGetRawTransaction to return btcjson.Error

Wrap *.BtcEncode errors into btcjson.Error when failing to encode wire
bytes to buffer
Updated createTxRawResult to use btcutil.SatoshiPerBitcoin
Cast SatoshiPerBitcoin const for createTxRawResult.
Add support for TravisCI.
Add TravisCI build status badge to README.md.
Have TravisCI build against both latest release and tip