hey, this all looks good but I'm not sure about this line.. it'll break if the graph container doesn't contain an id (and there's no reason the graph container needs to have an id). How about passing just `element` (i.e. `d3.custom.barchart(element)`) and doing `d3.select(el)` in line 2 of `d3.custom.barchart`? d3.select on a node returns the node, and this would also support passing an id (as `"#foo"`), because d3.select on a string does a query.