Apply the changeset from https://code.launchpad.net/~redtoad/pyopenssl/pyopenssl/+merge/178226 by Sebastian Rahlf
pyflakes and documentation cleanups
Further simplifications.
Add a changelog entry

Fixes #48
Merge pull request #78 from pyca/tsafe-apply-48

Replace the usage of `apply` in OpenSSL.tsafe with regular function call syntax.