Automatic clipExtent determination for mercator.

Since 3.1, the Mercator projection does not clamp y-values. For rendering
latitudes near the pole, the y-values can approach infinity. Rather than
clamping each point in the projection, d3.geo.mercator now sets the clipExtent
automatically (if not overridden) using the projection's scale and translate.
Fix #1160; remove redundant closing point.
Merge branch 'fix-closing-point'
Add test for clipExtent: redundant closing points.
Add a few missing imports.

These have no immediate effect since they're either redundant due to
being imported elsewhere, or they're not tested at the moment.
Updated package.json to include d3's license
Fix click suppression after dragend in cases where click doesn't fire.

Fixes Issue #1005 for both behavior.zoom and behavior.drag
More robust type inference for d3.interpolate.

Fixes #1180 #1179 #1176. Still a work in progress; needs a few more tests.
Favor strictEqual for testing.
Add missing import
Merge pull request #1182 from jfirebaugh/imports

Add missing import
Add Jason to official contributors list.
fix component support
Merge branch 'fix-component-support' of https://github.com/danmilon/d3 into fix-component-support
Move edits to src/component.js.
Merge branch 'master' of https://github.com/theoreticaLee/d3 into license
Move edits to src/package.js.
Ignore null geometries.
Merge branch 'fix-interpolate' into 3.1.5
Merge branch 'fix-null-geometry' into 3.1.5