ParentDimension shouldn't take margin from parents

Margins are already factored into the parent's positioning.
Adding option for rake samples:good[N] to start partway through list
Merge pull request #974 from shoes/good-samples-start-with

Adding option for rake samples:good[N] to start partway through list
Update JRuby to the newest and coolest release [ci skip]
Merge pull request #973 from shoes/background-fix

Background margins shouldn't pull from parent slot

Changelog: bugfix
Limit parent-dimensioned elements to their parent's bounds
Run background and border through positioning

Previously the background and border classes would *sometimes* skip out
on having their position applied by the slot. This, however, made the
elements themselves unnecessarily responsible for things like margins
applied from parents, and resulted in margins getting double-applied at
some points.

Now we always run these through positioning, but that revealed another
problem which was an endless loop of slot repositioning as the
background grew to fill its slot. Turns out that was a result of us not
excluding "spaceless" elements from our slot content height computation.
First methods on app-level click listener
Wire-up for SWT event listeners
Handle clicks and releases
Support removing an element's listeners
Small extraction and renaming
Don't allow click on hidden elements
Enable option to pass coordinates on click
Switch over to new app-level ClickListener
Merge pull request #977 from shoes/background-positioning

Run background and border through positioning

Changelog: bugfix
Merge branch 'master' into background-overflow-fix
Parent-dimensioned elements should obey margins

The calculated extent we were making didn't take the final margin of the
parent into account, so we had overruns in that direction (right or
bottom).
Extract methods for retrieving extents
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