copy() wrong behavior

[marcominetti]

@goldbuick reported:

if (resizeOk && this.pos >= this.buffer.length) {
var newBuffer = new Buffer(this.buffer.length * 2);
this.buffer.copy(newBuffer);
this.buffer = newBuffer;
}

also I encountered a bug here. this.buffer.copy doesn't handle default params properly in the browser. thus, it fills the newBuffer with zeros instead of the data from this.buffer.