Add t does_follow check for selfie and same user1 & user2.

Before:

$ t does_follow juanitofatas
No, @juanitofatas does not follow @JuanitoFatas.

$ t does_follow juanitofatas
No, @juanitofatas does not follow @juanitofatas.

After:

$ t does_follow juanitofatas
You cannot follow yourself!

$ t does_follow juanitofatas
"It's a same account!"
Merge pull request #180 from JuanitoFatas/patch/does_follow_selfie_check

Add selfie and user1 and user2 identical chekcs to does_follow command.