Run browser tests w/node v4
Run browser tests w/node v4

As zuul consequently fails when running on node v0.12.

phillipj/mustache.js,aaron-goshine/mustache.js,janl/mustache.js,janl/mustache.js,janl/mustache.js,janl/mustache.js,phillipj/mustache.js,janl/mustache.js,phillipj/mustache.js,phillipj/mustache.js,aaron-goshine/mustache.js,aaron-goshine/mustache.js,phillipj/mustache.js,aaron-goshine/mustache.js