Dynamic Series Branch, Rebased

This is just a rebase-and-remove-conflicts of the [dynamic-series](https://github.com/shutterstock/rickshaw/tree/dynamic-series) branch.  It is probably not ready to be merged into master, or I imagine that would have been done closer to the time of creation.  It does, however, work for me in the scenarios where I am using it.

If these changes are not ready for master, this branch could at least replace the current dynamic-series branch, giving a clean point for progress to continue from.  Whatever format is preferable, just let me know.

_Note: Pull request #211 also references this issue._