Add tests

tests/cases/fourslash/getOccurrencesOfDecorators.ts

@@ -0,0 +1,14 @@
+/// <reference path='fourslash.ts' />
+
+// @Filename: b.ts
+////@/*1*/decorator
+////class C {
+////    @decorator
+////    method() {}
+////}
+////function decorator(target) {
+////    return target;
+////}
+
+goTo.marker("1");
+verify.occurrencesAtPositionCount(3);

tests/cases/fourslash/quickInfoForDecorators.ts

@@ -0,0 +1,11 @@
+/// <reference path='fourslash.ts' />
+
+////@/*1*/decorator
+////class C {
+
+////}
+/////** decorator documentation*/
+////var decorator = t=> t;
+
+goTo.marker("1");
+verify.quickInfoIs("var decorator: (t: any) => any", "decorator documentation");