Continuing the discussion from Gemfile.lock vs Gemfile:
Aside from sprockets-rails and sass, there are other gems that are not the latest. A lot of them probably easily could be.
Here’s a list of the ones that look to me like they could be upgraded without issue:
There are some others that are out of date but from looking at the history are held back for specific reasons:
And a few others that are old simply because other gems depend on the older version, such as exifr and celluloid.
Still, the ones in the first list are probably fine. Would you be willing to try newer versions?