fix: allow zero-argument usage of Ember.isBlank, .isEmpty, .isPresent and .isNone

Fixes typed-ember/ember-cli-typescript#258
Fixes typed-ember/ember-cli-typescript#255
Fixes typed-ember/ember-cli-typescript#256
Fixes typed-ember/ember-cli-typescript#254

Author: mike-north

types/ember/index.d.ts

@@ -3117,22 +3117,22 @@ declare module 'ember' {
         /**
          * A value is blank if it is empty or a whitespace string.
          */
-        function isBlank(obj: any): boolean;
+        function isBlank(obj?: any): boolean;
         /**
          * Verifies that a value is `null` or an empty string, empty array,
          * or empty function.
          */
-        function isEmpty(obj: any): boolean;
+        function isEmpty(obj?: any): boolean;
         /**
          * Returns true if the passed value is null or undefined. This avoids errors
          * from JSLint complaining about use of ==, which can be technically
          * confusing.
          */
-        function isNone(obj: any): obj is null | undefined;
+        function isNone(obj?: any): obj is null | undefined;
         /**
          * A value is present if it not `isBlank`.
          */
-        function isPresent(obj: any): boolean;
+        function isPresent(obj?: any): boolean;
         /**
          * Merge the contents of two objects together into the first object.
          * @deprecated Use Object.assign

types/ember/test/utils.ts

@@ -14,6 +14,31 @@ function testIsNoneType() {
     }
 
     const anotherString = maybeUndefined + 'another string';
+    utils.isNone(); // $ExpectType boolean
+}
+
+function testIsBlank() {
+    utils.isBlank(); // $ExpectType boolean
+    utils.isBlank(''); // $ExpectType boolean
+    utils.isBlank('', ''); // $ExpectError
+}
+
+function testIsEmpty() {
+    utils.isEmpty(); // $ExpectType boolean
+    utils.isEmpty(''); // $ExpectType boolean
+    utils.isEmpty('', ''); // $ExpectError
+}
+
+function testIsPresent() {
+    utils.isPresent(); // $ExpectType boolean
+    utils.isPresent(''); // $ExpectType boolean
+    utils.isPresent('', ''); // $ExpectError
+}
+
+function testIsNone() {
+    utils.isNone(); // $ExpectType boolean
+    utils.isNone(''); // $ExpectType boolean
+    utils.isNone('', ''); // $ExpectError
 }
 
 function testMerge() {