add pytz to requirements for timezone support
refactor client a bit
* rename `latlon_or_address` to `assume_latlon_or_address`
* move `assume_latlon_or_address` from Directions to Client
* allow `_make_request` to not look for result key
PEP 8
add tests for new Timezones API endopoint
Add Timezone endpoint
new release of python-gmaps
update manifest template