Path to jsdoc binary is incorrect for node 4.x and npm 2.x

[This switch](https://github.com/softlayer/ember-cli-jsdoc/blob/master/lib/commands/ember-cli-jsdoc.js#L11) on the node process version to derive the path for the jsdoc binary produces an incorrect result in at least some cases. In our project that uses node 4.x and npm 2.x the correct path is `node_modules/.bin/jsdoc`.