OFB is specified as having an IV instead of a Nonce.

https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Output_feedback_.28OFB.29
ModeWithNonce is no longer used.
ModeWithNonce no longer exists.
OFB uses an initialization vector instead a nonce.
Use the version of PyPy from PPAs to get PyPy 2.1
Merge pull request #62 from dstufft/test-pypy

Enable testing on PyPy
Merge pull request #60 from dreid/ofb-iv-not-nonce

OFB uses an IV instead of a nonce.
API refactor to separate cffi declarations

* Moved to structure similar to OpenTLS
* api modified to load the cffi modules
* cffi verify methods broken out
* Jarret Raim and I pair programmed this
Various PR review fixes

* Changed some single quotes to double quotes
* Moved the files in the cffi package back into the openssl package
  * evp, opensslv
* Changed attrs from ALL CAPS
* Fixed up docstrings
* Stopped using fromlist=['*']
* No fallback on definition imports. You must supply includes, types,
  functions
* Change includes, types, functions to be strings rather than lists for
  now
* Removed teardown since we're not using it right now
remove import function, rename attrs to upper in modules
Merge pull request #67 from reaperhulk/api-refactor

API refactor to separate cffi declarations
Slightly clean up the OpenSSL binding

 - reduce the amount of state needed on the API instance
 - fixed import ordering
Inline this function, it didn't do much
Merge pull request #68 from alex/cleanup

Slightly clean up the OpenSSL binding
Camellia test vectors

* ECB tests come from the NTT Camellia pages (as linked to by the latest
  [CRYPTREC](http://www.cryptrec.go.jp/english/method.html)).
* CFB, OFB, CBC tests from OpenSSL evptests
Merge pull request #69 from reaperhulk/camellia-vectors

Camellia test vectors
add cryptrec and openssl test vector loaders + tests
sort the cryptrec loader dict's items to test reliably
crazy pep8 contortions
simplify and annotate loaders based on review feedback