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* Minor weaks and enhancements
* Switched to pbkdf2_ctypes for performance on passphrase stretching
* Moved all the coinop modules out of the useless `bit` and `crypto` subpackages. From now on, import directly from `coinop`
* Replaced PassphraseBox's dependency on NaCl SecretBox with a (AES-CBC-256 then HMAC-SHA256)
* Removed antiquated tests and installed tox config for testing and basic PassphraseBox tests
* Python 3.3+ compatibility