Remove connect-livereload dep & add semver check.

* Add `semver` check to prevent `npm install` from blowing up.
* Remove `connect-livereload` dep. This is built into the `grunt-contrib` tasks by now.
* Remove `yo` devDev. It's not used and caused warnings: 

```
npm WARN prefer global bower@1.2.7 should be installed with -g

npm WARN prefer global grunt-cli@0.1.9 should be installed with -g
```
* Remove `spawn: false` from `watch` task. This way `watch:livereload` can pick up the changes to `index.html` triggered by `watch:index`. This does make the livereload a little slower, but people could still change it if they wanted to.