Add OpenPGP operations using PGPy instead of BinGPG

[juga0]

• setup.py: add PGPy dependency
• init.py: bump version
• tests/conftest.py: add crypto maker
• autocrypt/crypto.py: OpenPGP operations with the same API as BinGPG
• tests/test_crypto.py: Tests for crypto.py, same API as test_bingpg.py This commit does not include crypto.py integration with with the rest of the files. To rest of code should continue working doing s/bingpg/crypto, but it's not done to have flexibility in the integration.

With respect to #5, changes are:

• do not overwrite any other file that is not needed to have crypto.py and its tests working
• remove comments
• remove logger
• remove passphrase protection possibility for private keys
• other refactoring

[hpk42]

Hey juga! this PR looks quite good, just two minor issues as commented inline. Happy to see integration of pgpy moving forward.

[juga0]

I'm rebasing to solve conflict with init.py. Which should be the version?, 0.4.1.dev1?

[azul]

Is there a need to bump the version? The new approach so far has not been exposed or included. I would tend to just add it and leave the version as is. But I am not familiar with versioning practices in python community. If you want to increase the version 0.4.1.dev1 seems to make sense to me.

[juga0]

Rebased and add new commit with the proposed changes. I don't know if it's preferred to rebase and ammend the new changes or to merge.

[azul]

@juga0 thanks a lot. I went through the fixup commits and they all look good. Rebased so easy to merge and tests are green. :green_heart: :smile: I'll go through the diff again and see if i spot sth. else and otherwise just merge.

[azul]

@juga0 Looks good. Thanks a lot!

[juga0]

Thank you