relax constraint on ridley to ~> 1.5

Ridley has been much more stable and should continue to be in the 1.x series
Merge pull request #786 from RiotGames/relax-ridley

relax constraint on ridley to ~> 1.5
Merge branch 'master' of https://github.com/RiotGames/berkshelf into 787

Conflicts:
	berkshelf.gemspec
	.git/MERGE_HEAD

	modified:   berkshelf.gemspec