Differences to ZX2C4’s pass

While passpy is fully compatible with [ZX2C4’s pass](http://www.passwordstore.org), there are some differences:

• As for the moment passpy does not print as many messages to the user, as pass does. Also some messages might be phrased differently.
• When invoking pass without any known command, show is used. passpy always needs to be given a command to invoke.
• passpy allows gen as a alternative to generate.
• After editing a password file with an editor pass notes the used editor in the git commit message. passpy uses the same message for updating a key, regardless if an editor was used or not. This is because for both cases passpy.store.Store.set_key() is being called which also handles the git commit.
• pass lists all files in the password store that do not start with a .. passpy only lists files that end on .gpg. The reason for this change is that the returned key names should be directly accessible with passpy.store.Store.get_key(), which expects a file ending on .gpg.