Added bindText + bindIcon for fluent construction.
Complain loudly if a null Animation is added to an AnimGroup

Raise an IllegalArgumentException if an attempt is made to add a null to an AnimGroup.  Without this, a NullPointerException is thrown downstream with no ability to locate the offending code.
Added bindEnabled().
Prepare for 1.7.2 release.
[maven-release-plugin] prepare release tripleplay-1.7.2
[maven-release-plugin] prepare for next development iteration
Force the native fields onto the POPUP_LAYER to ensure they're above everything.

This may very well not change anything, but is an experiment to see if this fixes some of our cases where fields appeared to be drawn behind (or possibly not at all) on certain machines.

And really, this is just more correct anyway.
Fix a bug where the window size was larger than requested on some platforms/themes.

Fancier Windows Vista/7 themes change the size of the window borders based on resizability of the window so we need pack() to happen last.
Move back to snapshot PlayN.
Split assets into separate submodule.
We should be setting _flipped here.
Move interaction machinery down to Widget.

Any widget might want to be interactive (aka tappable), not just text widgets.
Having the interaction code in Widget is pretty no-cost, because none of it is
called unless you call enableInteraction() in your ctor.
Bring SBT build up to date with various changes.
Be good and leave a deprecated ClickableTextWidget.
Add click() to Clickable.
Added a button that uses images for up/down state.

I'm not super thrilled with this because it can't extend Button and it's a
little annoying to have two different kinds of buttons in your code for code
that wants to operate indiscriminately on button like things.

Clickable doesn't really help because you want something that has Element's API
(setVisible, setEnabled) and Button's API (click, onClick, etc.).

It's also annoying to duplicate a non-trivial amount of code from Button. If I
had traits with self types, I could do all this properly. Or union types. Or
pink unicorns. Pink unicorns solve all problems.
New more abstract element parent: Container.

Elements is a Container, as will be another forthcoming container. This is
pretty internal, so hopefully this isn't going to break a bunch of clients.

I'm adding one new container, but this opens the door to other kinds of
containers which can now expose just the API they need, rather than extending
Elements and exposing an "I'm a list of elements" API in addition to whatever
sensible API they might have. (I'm looking at you Tabs.)
A new container type: Box.

It contains zero or one elements and passes things pretty much straight through
to its contents. This is useful if you have one "slot" in your UI that you want
to fill with, say, a "Loading..." label and then the real UI later, but you
don't want to have to pluck the Loading label out of its group and insert your
contents into the same index and blah blah.
Handle unready-image icon passed to ctor.

Prior to this, it was not triggering the addition of a Callback to the icon to
be notified when the image was ready.
Improve behavior when source image is smaller than bg space.