Fixing unit tests for User

The hours_worked method in the User class doesn’t consider punch times
in the future (which makes sense), but the tests didn’t account for
that, so they were changed to use times from a day before, so they
don’t randomly fail depending of the local time.
Updating Highcharts

Stats page now working, drawing lines and stuff (it didn’t before)
Cutting out DB trips in stats_controller index method

The stats page generates a pretty graph with hour counts from every
user. The corresponding controller method calls User#hours_worked for
every user, for every week since the start date hardcoded in the method
(2012-10-01) and for the entire period between the start date and
current time.

This commit changes two things: it removes the whole-period call and
instead uses the already found values from each week, applying a
reduction, and delegates the rounding of values to the JavaScript view.
Micro: using Foundation button bars for index

Buttons at bottom of index page now use a button bar from the included
Foundation framework, and are aligned and same-sized.
Improving stats page

Now allows to select period and specific user to see work track
Micro: changing user view form to show token

Requested by admins
Merge pull request #3 from redealumni/fixes_improvements

General fixes and improvements