Clearing filter from dimension on disposal and propagating to groups.

Previously, if a filter was present on a dimension, disposing of the
dimension would cause other dimension's group.all() counts to loose
sync with the filters. In certain circumstances, values of
group.all() would become negative.

crossfilter.js

@@ -1238,6 +1238,7 @@ function crossfilter() {
 
     // Removes this dimension and associated groups and event listeners.
     function dispose() {
+      filterAll();
       dimensionGroups.forEach(function(group) { group.dispose(); });
       var i = dataListeners.indexOf(preAdd);
       if (i >= 0) dataListeners.splice(i, 1);

src/crossfilter.js

@@ -710,6 +710,7 @@ function crossfilter() {
 
     // Removes this dimension and associated groups and event listeners.
     function dispose() {
+      filterAll();
       dimensionGroups.forEach(function(group) { group.dispose(); });
       var i = dataListeners.indexOf(preAdd);
       if (i >= 0) dataListeners.splice(i, 1);