Merge pull request #69 from reaperhulk/camellia-vectors

Camellia test vectors
lower ciphername, add api supports, improved assertion message

* supports method added to api to check if a ciphername is available.
  This will be used with skipif (and probably elsewhere)
* ciphername lowered. OpenSSL frequently supports aliases for various
  casing, but reliably supports all lowercase.
  (e.g. camellia-128-cbc, vs Camellia-128-CBC)
* When a cipher is not found an error will now be raised telling you
  what string cipher it couldn't find. This should probably become a
  real error like CipherNotFoundError.
show skipped test reasons via tox
camellia support

* This patch adds the Camellia block cipher
* New CRYPTREC loader (vectors in previous PR)
  - Provides ECB testing
* New OpenSSL loader (vectors in previous PR)
  - Provides CBC, OFB, CFB testing
* Tests will be automatically skipped if camellia support is not present
  in your OpenSSL library (OS X 10.8 will see this with default OpenSSL)
* Docs for the cipher