Added Variance and Corrected Standard Deviation to core array functions.
renamed sd to deviation #1073
added exit criteria for variance that returns NaN on an empty array
refactored results with NaN array and empty arrays to fit the results of R
using an evaulation array for accessor functions and ignoring NaN, undefined and null
d3.shuffle a subset of an array and tests for d3.shuffle.

d3.shuffle takes two extra optional arguments that work on array
subsets: d3.shuffle(array[, i0[, i1]]). If given just array, then
shuffles entire array. If given array and i0, shuffles from index i0 to
the end of the array. If given array, i0, and i1, shuffles between i0
and i1. Tests for d3.shuffle also added.

See #1865.
passing f to d3.mean function call in the variance implementation
Add ordinal rangeRoundPoints. Fixes #1760.
Add quadtree.find.
Simplify quadtree.find and add test.
Minor optimisation for quadtree.find.

Reduces branching a bit more.
Save a few bytes.
Save a few more bytes.

The removal of `k = i & 3` also seems to produce a slight speedup in
Firefox 29.0.1 according to a microbenchmark.
Fix #1609 - add transition "interrupt" event.

This is necessary for transitions to perform any cleanup in the case they are
interrupted (superseded) by another transition or an explicit interrupt.
Fix for re-entrant zoom gestures.

There are several conditions where a zoom gesture can begin while a zoom gesture
is already in progress. For example, you can use the mousewheel after starting a
drag gesture, or you can start a zoom transition interrupting another that is
already in progress. The zoom behavior now tracks concurrent zoom gestures so
that a zoomstart is only triggered at the very beginning, and a zoomend is only
triggered at the very end.
Add Canadian English locale.

Date and time formats as specified by CSA Z234.5:1989, implementing ISO 8601.
Add Canadian French locale.

Date and time formats as specified by CSA Z234.5:1989, implementing ISO 8601.
reimplemented variance to be calculated incremental using Knuth´s and Welford´s approach
returning `undefined` rather than `NaN` to comply with d3.mean as @mbostock suggested
retabbed with expandtab and tabstop=2