Revert "Worked around RubyGems 2.2.0 bug on Travis-CI"

This reverts commit 3ee8d615549b1dc14a0b187dece3ecef0b9309a8.
Merge branch 'rubygems-upgrade'

* rubygems-upgrade:
  Revert "Worked around RubyGems 2.2.0 bug on Travis-CI"

Conflicts:
	.travis.yml