Drop support for Python 3.3
ca_certs from environment HTTPLIB2_CA_CERTS or certifi
https://github.com/httplib2/httplib2/pull/117
PROXY_TYPE_HTTP with non-empty user/pass raised TypeError: bytes required
https://github.com/httplib2/httplib2/pull/115
Revert http:443->https workaround
https://github.com/httplib2/httplib2/issues/112
eliminate connection pool read race
https://github.com/httplib2/httplib2/pull/110
cache: stronger safename
https://github.com/httplib2/httplib2/pull/101