Merge pull request #8 from mlippert/widget-refactor

replace d3.last, add .gitignore, initial IWidget interface
removed unusued widgets.js call
legends now work when called with append
fixed up the label test page

just has labels and markers on it now, and it works again.  All
callouts tested on the tableCallout page.
Merge remote-tracking branch 'refs/remotes/upstream/master' into widget-refactor
cosmetic changes
1st pass at the label group widget