lib: don't print the error variable on a successful logout.
lib: don't show stars when typing the password.

Yes, I've changed my mind :)
lib: splitted the "performLoggin" function into two functions.

This way we separate the part where we interact with the user, and where we
interact with the server.
lib: added tests for the session.go file.
lib: removed debug message.
lib: actually save the contents of the topics.

Epic fail...
Added the diff and the status commands.

They haven't been implemented yet.
config: added bash completion.
Added the bash completion into the README file.