Upgrade boxen gem to 2.7.0 with Yosemite support

... including dependency on Puppet 3.7
Upgrade puppet modules for Yosemite support
Merge pull request #664 from boxen/yosemite

OS X 10.10 Yosemite support
Merge branch 'master' of https://github.com/boxen/our-boxen

Conflicts:
	Puppetfile
	Puppetfile.lock