Merge pull request #57 from tpkelly/master

Bubble/Point tweaks
Merge pull request #62 from tpkelly/master

Make tick marks default to shown
Added AMD support.
Added checks for dependencies: d3, d3.tip and crossfilter.
Merge pull request #63 from niksoper/master

Added support for AMD module loading (requirejs).
Added scatter series.
Added tests for x and y.
Updated default point size from 1 to 3.
removed transparency from scatter series points.
Made opacity of points configurable.
Merge pull request #64 from niksoper/master

Added scatter series