add transition.size
Add tests for transition.{size,node}.
Simplify the minimum sample distance check.

Rather than compute the distance from the start to the new middle, use the
already computed distance from the start to the end. Also, we no longer need the
additional check that the middle is close to either the start or the end because
this is covered by the minimum sample distance check.
Much larger minimum sample distance.
Invert logic.
Resample using a great-circle distance threshold.

Projections will typically exhibit less curvature at larger scales, with
geodesics becoming closer and closer to straight lines.  Using a minimum
angular distance for resampling therefore makes more sense than using an
arbitrary scale-dependent threshold.

It's not clear whether this new threshold should depend on the precision
parameter, or be configurable separately.
Much larger angular threshold.

Also, disable buffering to discard samples; all samples are retained.
Clarify comment.
Generalize d3_event_userSelect for dragging.

The new d3_event_dragSuppress method serves a similar purpose to the previous
d3_event_userSelect, except it generalizes to prevent all undesired browser
default behaviors when dragging. In addition to text selection, this includes
dragging (of links and images) and clicks (on links). Suppressing click events
is optional and can be controlled by the caller.
Inline d3_eventSuppress.
Merge branch 'add-transition-size' into 3.2.2
Merge branch 'drag-suppress' into 3.2.2
Update version.
Only bind relevant listeners on brush touchstart.

A mousemove event was being triggered on mobile Safari causing the brush
to jump briefly on touchstart, e.g. when viewing:

    http://bl.ocks.org/mbostock/raw/1667367/