Support Node 0.11

[mgol]

Node 0.11 is currently not supported and not even tested on. It should be added to the testing infrastructure with failures allowed and after all the issues are resolved, it should be tested & supported fully.

Node 0.12 is supposed to come soon so at least seeing what the issues may be should be done.

[oozcitak]

Node 0.11 build fails at memwatch: https://travis-ci.org/oozcitak/xmlbuilder-js/jobs/28787133 There is a standing issue and a PR to fix this.