Fix variable name bugs

Hi Jed,

I tried to use this component, but found some bugs caused by variable naming. The component was previously being defined as `Hammer`, which overwrote the Hammer JS module itself.

The module was also (I assume, incorrectly) exporting a variable called `Tappable`, rather than the component.

I switched these out and everything seems to work okay (:

I haven't done a version bump, as I see you have some tooling in Gulp to do that automatically.