Bugfix: Force TLSv1

This hotfix commit forces TLSv1 when submitting requests (POST and GET) to Keen IO.
Shamelessly stolen from StackOverflow's brilliant answers to the following:

http://stackoverflow.com/questions/18675872/requests-exceptions-sslerror-errno-8-ssl-c504-eof-occurred-in-violation-of
http://stackoverflow.com/questions/16883595/https-proxies-with-requests-errno-8-ssl-c504-eof-occurred-in-violation-of
http://stackoverflow.com/questions/14102416/python-requests-requests-exceptions-sslerror-errno-8-ssl-c504-eof-occurred