Fixed test ID selectors in docs and helper.

Author: mcibique

Diff for: README.md

@@ -262,7 +262,7 @@ In the next step you can make the selector little bit shorter by extracting part
 
 ```js
 function findByTId(tid) {
-  return findByCss(`[tid*='${tid}']`);
+  return findByCss(`[tid~='${tid}']`);
 }
 ```
 

Diff for: test/unit/utils/tid.js

@@ -12,9 +12,9 @@ let VueWrapperPrototype = Object.getPrototypeOf(dummyComponent);
 let WrapperPrototype = Object.getPrototypeOf(VueWrapperPrototype);
 
 WrapperPrototype.tid = function (selector) {
-  return this.find(`[tid="${selector}"]`);
+  return this.find(`[tid~="${selector}"]`);
 };
 
 WrapperPrototype.tids = function (selector) {
-  return this.findAll(`[tid="${selector}"]`);
+  return this.findAll(`[tid~="${selector}"]`);
 };