Apply patch Row chart enhancements

This PR does several things:
- first, I rebased this pull request: https://github.com/NickQiZhu/dc.js/pull/176 since its author didn't rebase for about 4 months. I claim absolutely no ownership of that code.
- second, I expanded upon it, adapted it to the current state of the code and API, and added some tweaks. Most notably, I added the possibility to specify whether or not the "Others" row should be displayed. This is so that the graph's scale is not completely messed up when the "top" results are still small compared to the total of Others.
- third, there seemed to be a problem with the elastic scaling of the rowChart's X axis. I changed it so that the axes are recomputed properly.

Please let me know if you need me to do anything else. Cheers!