Make lib and ffi be private on backend

Because now they are public on a binding instance if you need them!
Merge branch 'master' into privatize-me-captain

Conflicts:
	cryptography/hazmat/backends/openssl/backend.py
Merge pull request #388 from alex/privatize-me-captain

Make lib and ffi be private on backend
Revert "Travis now has an up to date pypy"

This reverts commit 5a4aa42542c952905fbf83582bff4bb2b328c4e1.
Merge pull request #390 from dreid/install-pypy-again

Revert "Travis now has an up to date pypy"
Merge branch 'master' into glossary-consistency