Support for box plot panels

This may be a bit unconventional for typical time series display, but I think it could be very valuable. Right now I emulate this by drawing a time series panel with line graphs with different percentiles. Together they provide information similar to that of a heat map. <img width="1413" alt="screen shot" src="https://cloud.githubusercontent.com/assets/156867/11131948/0e2953a2-8985-11e5-8c36-75083ed476b7.png"> <img width="233" alt="screen shot" src="https://cloud.githubusercontent.com/assets/156867/11719524/141a63da-9f53-11e5-8b93-e52bb564c04b.png"> And for better insight into data that has daily and weekly patterns, time series overlay help a lot to identify changes in data that always go up and down, but then you can compare it to how it was yesterday, and how it was the same day last week. <img width="1421" alt="screen shot 2015-11-12 at 21 44 57" src="https://cloud.githubusercontent.com/assets/156867/11132255/cd2e3eba-8986-11e5-8a90-42831687c88c.png"> I think box plots would better serve some of these cases. It does have the obvious draw back of flattening the "time" part of "time series", but one could render multiple ones. E.g. One for last 24 hours, and one for the 24 hours before that, similar to Graphite `summarize(24h)`. Example box plot from https://codeascraft.com/2015/11/10/q3-2015-site-performance-report/