Add support to DivIcon for reusing a div. Fixes #1753. Still issues remain (Can't change a marker with a DivIcon to have an image Icon or vice versa)
Make Icon/DivIcon reuse not try reuse the wrong dom element type.
Don't say this so much, options is in local scope.
Make Marker setIcon unit tests better.
Tidy up ugly icon-swap code.
jshint fixes.
Merge pull request #1754 from danzel/master

Fix SetIcon with DivIcons