Updated unzip to 0.1.6

There were problems with node-unzip 0.1.4 and node 0.10.0. When installing a
component that requires unzip, installation would terminate with error message:

    TypeError: listener must be a function
        at TypeError (<anonymous>)
        at Parse.EventEmitter.once (events.js:171:11)
        at Extract._write (/Users/satazor/Work/twitter/bower/node_modules/unzip/lib/extract.js:59:23)
        at doWrite (_stream_writable.js:211:10)
        at writeOrBuffer (_stream_writable.js:201:5)
        at Extract.Writable.write (_stream_writable.js:172:11)
        at write (_stream_readable.js:547:24)
        at flow (_stream_readable.js:556:7)
        at ReadStream.pipeOnReadable (_stream_readable.js:588:5)
        at ReadStream.EventEmitter.emit (events.js:92:17)

These problems have been fixed in 0.1.6. You can read more about this discussion
at https://github.com/nearinfinity/node-unzip/issues/20#issuecomment-15752755.