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.