Performance testing for dygraphs.

To measure times on a benchmark, run:

git clone https://github.com/danvk/dygraphs.git
git clone https://github.com/danvk/dygraphs-perf.git
cd dygraphs-perf
./perf.sh

This will print out something like:
1000/100/10: 525, 523.7+/-20.6 ms (540, 496, 546, 518, 554, 532, 495, 515, 507, 534)

This means that it ran a benchmark where it drew a chart with
- 100 series
- 1000 points per series

It created and drew this chart 10 times to get ten elapsed times. These are
listed in parentheses, in ms. The first number after the colon is the median, followed
by mean +/- std. dev.

If you want to run with different combinations, tweak the perf.sh script.

This script is maintained outside of the dygraphs repository because it's
useful to run git commands in the dygraphs repository (i.e. reset to an old
commit) without having them affect the benchmark scripts.