Always use system ruby on Travis
Always use system ruby on Travis

- Now that Travis is on Mavericks, this is the correct thing to do
- ARCHFLAGS needed due to https://github.com/pivotal-sprout/sprout-wrap/issues/36
[#69812122]

pivotal-sprout/sprout-exemplar,wendorf/sprout-exemplar,andrewmacgregor/sprout-custom,pivotal-sprout/sprout-exemplar,minifast/sprout-app,minifast/sprout-app