add user group link
[#106] upgrade d3 to v3
Merge branch 'master' of github.com:NickQiZhu/dc.js

Conflicts:
	dc.min.js
rename d3.v2.js to d3.js
upgrade to d3.v3
optimize example html files
upgrade d3 -> 3.0.7 & crossfilter -> 1.1.1
Merge branch 'gh-pages-dev' into gh-pages

Conflicts:
	crime/index.html
	index.html
	js/d3.js
	js/dc.js
	vc/index.html
cache x unit count and improve example page focus performance
dc.js v1.2 release
Merge branch 'gh-pages' into gh-pages-dev

Conflicts:
	js/dc.js
update d3 and crossfilter