Update handling of limit to the current es6 draft.

Author: jdalton

lodash.js

@@ -13568,7 +13568,7 @@
         separator += '';
         if (separator == '' && reHasComplexSymbol.test(string)) {
           var strSymbols = stringToArray(string);
-          return limit === undefined ? strSymbols : strSymbols.slice(0, limit < 0 ? 0 : limit);
+          return limit === undefined ? strSymbols : strSymbols.slice(0, limit >>> 0);
         }
       }
       return string.split(separator, limit);

test/test.js

@@ -23251,7 +23251,7 @@
         thumbsUp = '\ud83d\udc4d';
 
     QUnit.test('should account for astral symbols', function(assert) {
-      assert.expect(32);
+      assert.expect(33);
 
       var allHearts = _.repeat(hearts, 10),
           chars = hearts + comboGlyph,
@@ -23274,7 +23274,8 @@
       assert.strictEqual(_.size(string), 13);
       assert.deepEqual(_.split(string, ' '), ['A', leafs + ',', comboGlyph + ',', 'and', rocket]);
       assert.deepEqual(_.split(string, ' ', 3), ['A', leafs + ',', comboGlyph + ',']);
-      assert.deepEqual(_.split(string, undefined), string.split(undefined));
+      assert.deepEqual(_.split(string, undefined), [string]);
+      assert.deepEqual(_.split(string, undefined, -1), [string]);
       assert.deepEqual(_.split(string, undefined, 0), string.split(undefined, 0));
 
       var expected = ['A', ' ', leafs, ',', ' ', comboGlyph, ',', ' ', 'a', 'n', 'd', ' ', rocket];