Add the easy way to fill the source URLs

[fflorent]

Typing the URL in a smartphone is pretty hard.
It should be easy to fill it. We can first help to fill an URL to a text file hosted on Github. To do so:

• The user enters a Github account
• Display the account's repositories
  • If a repository is named "Fortune", check it by default and display it at the top of the screen
  • The user clicks on next
• Show the tree of the files (with a *.txt filter) and the directories. The user can check one or many txt files.
• If the user clicks on a file, display the content of that file.
• Once the user has chosen the fortunes they wanted, go back to the option screen, with the selected sources

Florent