Warn if installing on older Node.js version than supported

This will produce a warning when this library is installed on a system with node.js version below 0.10. See [NPM#Engines](https://www.npmjs.org/doc/files/package.json.html#engines).

This is yet another PR based on the discussion and issue described on [this SO question](http://stackoverflow.com/questions/25579734/nodejs-google-api-module-typeerror-cannot-read-property-prototype-of-und/25584308?noredirect=1#comment39984308_25584308) (and your comment).