Py-geohex3

* Add Python3 support:

* Change division operator for Python2 and Python3 compatible
* Add `tox.ini` for multiple env tests
* Add py3.3 to `.travis.yml` for test Python3.3
* Add py3.5 to `.travis.yml` for test Python3.5
* Add pypy to `.travis.yml` for test PyPy
* Fix PEP8 violation
* Fix `ResourceWarning: unclosed file` warning

* add functions below:

* get_xy_by_location
* get_zone_by_xy
* loc2xy
* xy2loc
* adjust_xy

* Ported GEOHEX V3.2 algorithm from JavaScript version (original version)