export force.drag instance so user can access it by calling force.drag() with no arguments; the drag events have been namespaced as <event>.force, similar to the other force events: mouseover.force and mouseout.force.
force layout: properly UNSET the .fixed bits: user may be using further bits and those should be kept intact.
Allow projection.invert to return null.

Previously this would throw errors.
README.md: Point hyperlinks at github explicitly

Using relative hyperlinks here results in some weirdness when the
readme is displayed on npmjs.org.

If this patch lands, I'd suggest also doing `npm publish -f` (or
just bump the version in package.json and `npm publish` un-forcefully.)
Fix for duplicate keys in selection.data.

Fixes #997. The enter, update and exit selections are now initialized as fixed-
length arrays rather than dynamically populated with nulls. If duplicate keys
are used for either data or selected elements, only the first datum or element
is considered and subsequent data or elements are ignored.
Add test and fix for duplicate keys.
Simplify.

The length of the exit selection is always the same as the length of the
original selection, independent of the data, so there is no need to compute the
maximum of the two lengths.
Merge branch 'patch-1' of https://github.com/isaacs/d3 into 3.0.3
Merge branch 'fix-duplicate-keys' into 3.0.3
Merge branch '3.0.3'
Fix big with constant greatArc target.

The local variable `t` was masking the private field of the same name. The use
of single-letter variables is preferred for smaller scopes.
Merge branch 'fix-greatarc-target'
Add major & minor extent and step to graticule.

Fixes #1009.
Default graticule step is now 10°. Better tests.
Remove unnecessary argument.
Move tick class to the g element. Fixes #1016.
Enter domain path prior to update transition.

The update transition must be created after the domain path is entered, or else
the entering domain path will not be part of the update transition, and thus
will not have the "d" attribute computed correctly. Fixes #1022. This bug was
introduced by 8ee6c126bcdc3f9965457b411794e9ae7c5972ec to squash a warning!
Simplify d3.random.logNormal. Fixes #787.
Deprecate d3.geo.greatArc; add d3.geo.distance.

Now that D3 supports great-arc interpolation automatically for projections,
there is no need for a great arc feature generator, as a simple LineString
geometry object is equivalent. For the same reason, d3.geo.graticule does not
need to use supersampling on meridians, since meridians are great arcs.

This commit also adds d3.geo.distance(a, b) for computing the length of the
great arc between points a and b in radians, as a replacement for the
deprecated d3.geo.greatArc method, and a faster alternative to constructing a
d3.geo.interpolate solely to measure distance.

Fixes #1021 #1024.
Upgrade dependencies; remove Sizzle dependency.