added support for curvedLines plugin (addresses issues #90 and #33)
support could be improved by distinguishing between real and interpolated data points, but I can't find anything in the data to makes this distinction. it could be that we'd have to change that in the native curvedLines plugin before that would happen.
added a copy of the latest curvedLines.js plugin the local repo
added examples/curved-lines.html and added CL to list of supported plugins in README
organized examples/index.html into basic functionality and plugin support as separate categories