Make toEqual matcher report the difference between objects

- Mismatches deep within object/array structures are pinpointed with a JsonPath-like syntax.

src/core/matchers/NullDiffBuilder.js

@@ -0,0 +1,10 @@
+getJasmineRequireObj().NullDiffBuilder = function(j$) {
+  return function() {
+    return {
+      withPath: function(_, block) {
+        block();
+      },
+      record: function() {}
+    };
+  };
+};