bigbuffer

Using list of buffer to construct a BigBuffer to break through nodejs's buffer size limitation (1G)need install mocha

npm test

```coffee-script BigBuffer.fromFile "bigFile",(err,bb)->

console.assert bb.length # is buffer length
# get a normal buffer
buffer = bb.slice(0,10)
# get byte at index
byte = bb.byteAt(1000)

```