Add support for %cat with .rb ext omitted.
Allow highlighting ommitted '.rb' ext, DRY up ext checking.
Only call Pry::Code#from_file once on instantiation.
Oops, fix typo in comments.
Switch to backticks instead of plusses.
Set and unset in a context.
Remove unnecessary #basename.
Remove early File#basename so relative paths actually work.
* removed most historicla junk from lib/pry/test/helper.rb
* relocated recalcitrant junk to the local spec/helper.rb (this isn't exposed to 3rd parties)