lib/rbreadline: Replace DL with Fiddle.

This removes usage of the now-deprecated DL in favour of Fiddle. Fixes
deprecation warnings when running under Ruby 2.0 and newer.
lib/rbreadline: Remove the stupid from @proto assignment statement

This cleans up the way in which @proto is set so as to avoid the nasty
crud that it originally used in order to get the desired result.
Merge pull request #90 from Olipro/switch-to-fiddle-from-dl

lib/rbreadline: Replace DL with Fiddle. Also fixes #87