Added test for JSX spread properties.

Author: DanielRosenwasser

tests/cases/fourslash/tsxCompletion4.ts

@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+//@Filename: file.tsx
+//// declare namespace JSX {
+////     interface Element { }
+////     interface IntrinsicElements {
+////         div: { one; two; }
+////     }
+//// }
+//// let bag = { x: 100, y: 200 };
+//// <div {.../**/
+
+goTo.marker();
+verify.completionListContains("bag");