YarnInstaller uses latest yarn
YarnInstaller uses latest yarn

No longer needs a default version

[#141167599]

Signed-off-by: Keaty Gross <ba27100af1ae477f2abedd28f15b1dd208b1f48a@pivotal.io>

cloudfoundry/ruby-buildpack,ekaranto/rails4-bluemix-buildpack,ekaranto/rails4-bluemix-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,ekaranto/rails4-bluemix-buildpack,ekaranto/rails4-bluemix-buildpack,cloudfoundry/ruby-buildpack