drop Python 2.7 support

Python 2.7 EOL is arriving on 2020-01-01: https://pythonclock.org/

This will allow us to use Python 3 only libraries, like python-barcode,
which can maintain a reduced, simpler codebase, due to only one version
to support.

Closes #371.

Signed-off-by: Romain Porte <microjoe@microjoe.org>

examples/weather.py

@@ -13,7 +13,6 @@
 # Check out his github: https://github.com/AdamWhitcroft/climacons
 
 
-from __future__ import print_function
 from datetime import datetime
 import calendar
 import urllib