Run TravisCI against Node.js v0.10

Ensure that each commit is vetted with the latest stable version of
Node.js.
Run CI against Node v0.11 as an allowed failure

Building against the latest unstable release of Node.js should help the
project stay on top of any bugs or breaking changes in the platform.
Specifying that job as an allowed failure guarantees that errors do
not block ongoing work for officially-supported releases.
Merge pull request #415 from jugglinmike/test-against-node-11

Increase platform coverage on TravisCI