Changed text output if no new messages
Added support for file sending to CLI
Fixed restricted name in unit test
Changed hash from SHA256 to SHA512
Changed version to 0.2.6
Various fixes to improve security

* Changed fuzzy test sizes
* Changed hash to SHA512
* Removed unnecessary PBKDF2
Various fixes
* Changed default box name to "box"
* Changed package modules versions
Fixed wrong cli usage text
Small syntax fix
Added Python 3 support to CLI
Changed AES mode to CFB
Removed PKCS#5 padding
Changed README.md
Some minor fixes.
Changed CHANGELOG