Update to match latest version of Hammer

Internals of Hammerjs [changed](https://github.com/EightMedia/hammer.js/blob/fc6b1c23b61be607650497f4902ad8c4abd5e7e2/src/instance.js#L39). Old `unbind` code is no longer working with latest releases of Hammer and throws an exception when unbinding, which unfortunately stalls the page...