Exceptions

See #34.
To prepare #75.
More Exceptions

- Added more Exceptions
- Added exception to documentation headers
Missing doc
Missing doc
Missing doc
More Tests (149)

Fixes #75.
- Added more tests
Note: some tests are still missing, but i think the API is now save.

Run travis, run!
ChaCha20

- Added GenerateNonceChaCha20
- Added EncryptChaCha20
- Added DecryptChaCha20
- Added related tests
- Updated README
Merge pull request #80 from bitbeans/master

Docs / New Exception Types / ChaCha20 / More Tests