fix(except): special treatment for string

Author: rickardvh

Diff for: src/enumerable.ts

@@ -477,7 +477,7 @@ export class Enumerable<T> implements Iterable<T> {
    */
   public except(iterable: Iterable<T>): this;
   @parse((_thisRef: Enumerable<T>, itemOrIterable: T | Iterable<T>) => {
-    if (!Utils.isIterable(itemOrIterable)) {
+    if (!Utils.isIterable(itemOrIterable) || typeof itemOrIterable === 'string') {
       return [(x: T) => x !== itemOrIterable];
     }
     const set = new Set(itemOrIterable as Iterable<T>);

Diff for: src/test/enumerable.spec.ts

@@ -1256,8 +1256,8 @@ describe('Enumerable', () => {
       expect(new Enumerable([1, 2, 3]).except(0).toArray()).toEqual([1, 2, 3]);
 
       jsc.assertForall(
-        jsc.array(jsc.nat), jsc.nat,
-        (xs: number[], a: number) =>
+        jsc.array(jsc.string), jsc.string,
+        (xs: string[], a: string) =>
           !new Enumerable(xs).except(a).contains(a)
       );
     });