Sketch of floating keyword input with fatal flaw

Flaw that is fatal: "Show all kanji" button doesn't trigger any of the
float-magic :(

ALSO: people will hit "Enter" key on floating keywords and that is a big
nicht-nicht presently
Now "Show all kanji" participates in all the fun!

Flaw: reducing Heisig number breaks the hovers, even for recognized
kanji that are still recognizable
PartialFix for #12
Almost there

Two more things to fix: enter; green when resurrected.

Damn, maintaining state when Heisig number decreased added a lot of
complexity. Learned about `bind` and junk.
Enter on inputs no longer submit forms yay!

This was a PAIN to fix. Apparently d3.selectAll().on("submit",...) won't
actually stop the form from proceeding, even with stopPropagation. So I
used plain Javascript to accomplish the deed. Think about filing a
bugreport with D3.
Slightly better CSS for floating keyword
Added basic keyword success tracking
CSS tweak for Firefox

Can't really find a good way to make the width of the keyword hover fit
the contents (input box and X delete icon)...