Upgrade Requests to 1.2.3; #43

This repins requests in requirements.txt. The change is so minor that I
can't imagine Requests 1.1.0 wouldn't still work, but it seemed better
to stick with pinning and let advanced users manually use an older
Requests version as necessary.
Bump version number per @mjallday; #46
Merge remote-tracking branch 'whit537/requests-1.2.3'