quote node.js versions for travis 

See https://github.com/visionmedia/mocha/commit/a8c67e95bfb569d51dbb69dad7952a587b6b92d7 .

YAML parses `0.10` as "0.1", so without quotes it could cause trouble.
Merge pull request #73 from rlidwka/patch-1

quote node.js versions for travis