Hover for tabris "string"

[angelozerr]

Tabris uses a lot of string to define widget type, event, etc. It should be cool when mouse hover those string, it displays the doc of the widget, action. Here a screenshot, when mouse hover the "Button" string inside tabris.create :

[angelozerr]

@cpetrov I have implemented hover for widget type (string inside tabris.create like the previous screenshot).

If you have time, it should be cool if you could implement for other type like event, etc inside findTypeAt https://github.com/angelozerr/tern-tabris/blob/master/tabris.js#L199