Merge branch 'master' into add-crt-coefficients

* master:
  Also clean up this syntax
  Fixed a missing word in the RSA docs
  Fix comments in padding.py to be accurate
  add versionadded to cast5
  A few style nits in the docs
  add CAST5 support to changelog
  Changed .... lines to ~~~~ and s/Gnu\/Linux/Linux/
  Pypy is not a real word either apparently.
  Added Pypy note and fixed libffi's "spelling"
  Added Debian mention, extra missing packages
  Added a docs section on Linux installation
  remove some extra linebreaks
  add cast5 docs
  Syntax highlight the go code. Be mad Rob Pike.
  add cbc, cfb, ofb support to CAST5 (aka CAST128) for openssl & cc
  re-add CAST5 ECB support (OpenSSL & CC backends). fixes #417
  Switch this to a warning block
  Be clear about HKDF's applicability for password storage

Conflicts:
	docs/hazmat/primitives/rsa.rst