Update gregorio-mode.rcp

Improved recipe
Merge pull request #1443 from cajetanus/patch-1

Update gregorio-mode.rcp
added recipe for spotify's dockerfile-mode
Merge pull request #1444 from andreasjansson/master

added recipe for spotify's dockerfile-mode
New recipe: ido-better-flex.rcp
ido-ubiquitous.rcp: use github instead of from elpa