incremental approximate histograms
Merge pull request #3 from d2fn/master

dynamic histograms
merge categories
weighted incremental computation of mean and variance

From
http://www-uxsup.csx.cam.ac.uk/~fanf2/hermes/doc/antiforgery/stats.pdf.
Merge pull request #4 from masverba/incremental-mean-variance

weighted incremental computation of mean and variance
Approximately Detecting Duplicates for Streaming Data using Stable Bloom Filters - Fan Deng, Davood Rafiei 2010
Finding Frequent Items in Data Streams - 2004
Add CountMinSketch
Merge pull request #5 from emad/master

Approximately Detecting Duplicates for Streaming Data using Stable Bloom...
Merge pull request #6 from blinsay/cmsketch

Add CountMinSketch
add HLL in practice paper
Merge pull request #7 from ztellman/master

add HyperLogLog in Practice paper
streaming quantile computation