Don't require an additional method to draw with D3

[mattdodge]

There is some discussion about this on #145 already, but in order to make a D3 chart work you need to do the following:

var chart = new Epoch.Time.Line({ ... });
chart.draw();

In jQuery, no draw call is necessary. They should probably work the same (at least the D3 method should be documented if it will remain different).