Allow records to be removed.

This adds a new method to all crossfilter instances, allowing the
currently-selected records to be removed, e.g.

  var db = crossfilter([1, 2, 3]),
      dimension = db.dimension(Number);
  dimension.filter(1);
  db.remove(); // removes a single record (1), leaving [2, 3]
Rename {dimension,group}.remove to dispose.

The remove methods are kept for backwards-compatibility.
Version 1.3.0.

The version number is now derived from package.json.

UglifyJS and D3 dependencies have also been updated.
Fix issue with updating index after removing data.

Fixes #89.
Fix data removal when group cardinality ≤ 1.

Fixes #90.
Fix filterFunction followed by filterRange.

Fixes #93, #94.
Remove stale groups on data removal.

Previously, groups would never be removed even if the values that
created them were removed.

Fixes #91.
Fix reindex and group listeners on data removal.

There was a bug where the new index was not always being copied.  In
addition, the updateMany/updateOne/null behaviour, was not being updated
for groups on data removal.