Fix orList to be the same as in JS and follow the chicago style for commas

Author: danez

src/Utils/Utils.php

@@ -500,7 +500,7 @@ public static function orList(array $items)
             range(1, $selectedLength - 1),
             function ($list, $index) use ($selected, $selectedLength) {
                 return $list.
-                    ($selectedLength > 2 && $index !== $selectedLength - 1? ', ' : ' ') .
+                    ($selectedLength > 2 ? ', ' : ' ') .
                     ($index === $selectedLength - 1 ? 'or ' : '') .
                     $selected[$index];
             },

tests/Utils/QuotedOrListTest.php

@@ -47,7 +47,7 @@ public function testReturnsTwoItemList()
     public function testReturnsCommaSeparatedManyItemList()
     {
         $this->assertEquals(
-            '"A", "B" or "C"',
+            '"A", "B", or "C"',
             Utils::quotedOrList(['A', 'B', 'C'])
         );
     }
@@ -58,7 +58,7 @@ public function testReturnsCommaSeparatedManyItemList()
     public function testLimitsToFiveItems()
     {
         $this->assertEquals(
-            '"A", "B", "C", "D" or "E"',
+            '"A", "B", "C", "D", or "E"',
             Utils::quotedOrList(['A', 'B', 'C', 'D', 'E', 'F'])
         );
     }

tests/Validator/FieldsOnCorrectTypeTest.php

@@ -322,7 +322,7 @@ public function testOnlyShowsOneSetOfSuggestionsAtATimePreferringTypes()
     public function testLimitsLotsOfTypeSuggestions()
     {
         $expected = 'Cannot query field "f" on type "T". ' .
-            'Did you mean to use an inline fragment on "A", "B", "C", "D" or "E"?';
+            'Did you mean to use an inline fragment on "A", "B", "C", "D", or "E"?';
 
         $this->assertEquals($expected, FieldsOnCorrectType::undefinedFieldMessage(
             'f',
@@ -338,7 +338,7 @@ public function testLimitsLotsOfTypeSuggestions()
     public function testLimitsLotsOfFieldSuggestions()
     {
         $expected = 'Cannot query field "f" on type "T". ' .
-            'Did you mean "z", "y", "x", "w" or "v"?';
+            'Did you mean "z", "y", "x", "w", or "v"?';
 
         $this->assertEquals($expected, FieldsOnCorrectType::undefinedFieldMessage(
             'f',