Fixes #1024 -- a utility function for checking an implementor against an ABC
whoops, forgotten file
Added header
py3k fix
Fix for abstractproperty, and make things nicer
fix up the line coverage
Merge branch 'master' into verify-interfaces

Conflicts:
	cryptography/utils.py
Statically verify interface implementations, and fix all the resulting bugs
fixed some naming in the tests
Merge branch 'master' into verify-interfaces

Conflicts:
	tests/hazmat/primitives/test_hmac.py
bump the point releases we test against
filter backends during initial generation to elide tests entirely
reorganize try block for test generation
make sure pyenv is up to date
Merge branch 'master' into verify-interfaces

Conflicts:
	cryptography/hazmat/primitives/hmac.py
Fixed #1436 -- mark the multifernet tests as requiring the backends they need
add comment explaining some weirdness
Refactor our creation of CFFI FFI and libraries slightly.

Centralize everything for ease of use.
Update test for new API
Also switch to the explicit verifier construction approach, so the diff for disabling implicit compile is even shorter