Now inside the <template> of a SkyElement you can use
on-eventName="method" on any element to add event listeners.
For example you can write <sky-button on-click="handleClick">
and then define handleClick(event) on the element class that
contains the button.
In adding this and tests I also realized that property bindings
were not setup on the initial call to bind(), which is now
fixed in this patch (See change to Node.prototype.bind).
R=eseidel@google.com, rafaelw@chromium.org
Review URL: https://codereview.chromium.org/812713005
Eventually we'll want to replace these with something
fancier like polymer, but this exercise helped us
find several bugs in the engine as well as
removed one more blocker from using Sky to
replace mojo/views usage in mojo/examples.
R=esprehn@chromium.org
BUG=443439
Review URL: https://codereview.chromium.org/809233002
