Fix #121; respect truthiness of filterFunction.

Author: jasondavies

crossfilter.js

@@ -1,5 +1,5 @@
 (function(exports){
-crossfilter.version = "1.3.7";
+crossfilter.version = "1.3.8";
 function crossfilter_identity(d) {
   return d;
 }
@@ -825,7 +825,7 @@ function crossfilter() {
           removed = [];
 
       for (i = 0; i < n; ++i) {
-        if (!(filters[k = index[i]] & one) ^ (x = f(values[i], i))) {
+        if (filters[k = index[i]] & one ^ !(x = f(values[i], i))) {
           if (x) filters[k] &= zero, added.push(k);
           else filters[k] |= one, removed.push(k);
         }

crossfilter.min.js

@@ -1,6 +1,6 @@
 {
   "name": "crossfilter",
-  "version": "1.3.7",
+  "version": "1.3.8",
   "description": "Fast multidimensional filtering for coordinated views.",
   "keywords": [
     "square",

package.json

@@ -297,7 +297,7 @@ function crossfilter() {
           removed = [];
 
       for (i = 0; i < n; ++i) {
-        if (!(filters[k = index[i]] & one) ^ (x = f(values[i], i))) {
+        if (filters[k = index[i]] & one ^ !(x = f(values[i], i))) {
           if (x) filters[k] &= zero, added.push(k);
           else filters[k] |= one, removed.push(k);
         }