Uses grunt-contrib connect as a static server

This PR contains a number of small changes related to the development environment:

One question about how the Ionic repo should be used: Is it only supposed to be used to build Ionic, or is it thought as a base for applications?

There are (IMO) indications for both in the structure of the repo:

* The `dist` folder indicates that it is meant to be used to build applications
* But there is no `index.html` inside it
* The `Gruntfile.js` doesn't show any task apart from builing the Ionic framework
* As a developer, and as per the documentation, I would love to use the SASS files to customize Ionic.


--

* Uses grunt-contrib connect as a static server
* Sets server as the default grunt task
* Removes useless `concat` task in `watch:sass`
* Add `repository` field in `package.json`