Use readline to manage the prompt

* Use arrows to navigate in the history
* Standard movements commands are available (C-a, C-e, C-l, ...)
* Standard killing commands are available (C-k, C-w, ...)

See http://cnswww.cns.cwru.edu/php/chet/readline/readline.html
Improve text formatting function
Use GNU readline
Merge pull request #25 from MiLk/features/readline

Use readline to manage the prompt