Fix temperature reporting

This fixes the currently broken temperature reporting as described in issue #93.
This changes the ABI, as the `psmove_get_temperature_in_celsius` function now returns an `int` instead of a `float`. Applications linked dynamically against old PS Move API versions will break.

I suggest you just change this back to `float` (and also the SWIG bindings and the C example) and then cast the return value to `float` in the implementation below, this would keep the ABI while fixing the return value in degree celsius (also change celcius to celsius -> the original documentation contains a typo there).