Added function to get block based on a block locator.
Added function to get block based on a block locator.

javascriptit/bitcoinjs-server,bitfloor/bitcoinjs-server,dazoe/bitcoinjs-server,dazoe/bitcoinjs-server,dazoe/bitcoinjs-server,bankonme/bitcoinjs-server,zhangweis/node-jds,bankonme/bitcoinjs-server,javascriptit/bitcoinjs-server,bitfloor/bitcoinjs-server,javascriptit/bitcoinjs-server,zhangweis/node-jds,bankonme/bitcoinjs-server,zhangweis/node-jds