Update of sprockets gem to fix CVE-2014-7819

Commit also updates some other gems as well and
removes uber (bundle update was used).
Revert "Fix sprockets file exposure vulnerability"

This reverts commit 17c666c8dc39a482ca8afa6f3c3fb048ed6428a0.

The fix is not needed anymore if sprockets 2.2.3 is used.
Merge pull request #2147 from opf/hotfix/update_sprockets_version

Update sprockets version to address CVE-2014-7819