Upgrade CacheControl to 0.10.2

This fixes a reference cycle issue where pip would randomly hang
forever in some of the tests.
Merge pull request #1915 from dstufft/upgrade-cachecontrol

Upgrade CacheControl to 0.10.2
Clean up some no longer needed compatability code
Merge pull request #1901 from dstufft/cleanup-compat-wtf

Use b"" instead of b()
Fix #1657 - Explicitly close the requests session