add wordtree plugin
Added README with demo link to bullet chart
Merge pull request #26 from reidab/bullet_readme

Added README with demo link to bullet chart
Update geom/contour/README.md
Update geom/contour/README.md
Rewrite d3.hexbin.
Add hexbin README.
Tweak README.
Tweak README.
Make hexbin API consistent with D3's histogram.
Fix parens.
Fix typo.
Update hexbin/README.md
Update README.
Add Peirce Quincuncial projection.
Enable clipping on Peirce quincuncial.
Add d3.geo.dymaxion plugin.
Cleanup.
Cleanup rotation.
Cleanup.