Clarifies where to find the releases

Resolves issue #644
Merge pull request #645 from spuder/patch-1

Clarifies where to find the releases
Add Ruby 2.1.2 to the README
Merge pull request #656 from adamnbowen/patch-2

Add Ruby 2.1.2 to the README
Typo
Merge pull request #658 from gfestari/typo

Typo
bump boxen-xquartz to 1.2.1
Merge pull request #663 from MarkVillacampa/master

bump boxen-xquartz to 1.2.1
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
upgraded boxen