Fix bigintToBuffer formatting for positive values with high bit set.
Fix bigintToBuffer formatting for positive values with high bit set.

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