Adds tooltips for team members description

This refers to issue https://github.com/euruko2013/site/issues/48.

I have added the following functionality.

* Added jQuery plugin **powerTip** for tooltips (CSS/JS files)
* Changed layout.html.erb to **load the plugin** files
* Changed index.html.erb to **add team description**
* Changed main.coffee to **add the event** initializer for the tooltip to work
* Changed some CSS to make the tooltips **more readable**

Planned for next commits
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* Support for mobile devices
* Add @fotos  team description