Interpolated id fix and more

I did the following updates:
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FIXED: changeZoomLevel signature [README.md]
FIXED: using an angular binding (id={{myId}}) for panzoomId didn't work …
ADDED: karma test to cover this case
ADDED: config.inverMouseWheel option that will invert mousewheel direction
if set to true (defaults to false)
UPDATED: bin files with a copy of build files (guess there's no gulp task for that ?)

I also fixed a couple of jshint errors, no idea if I introduced them or if there were there before.