Use Jest as the test framework

- Remove mocha, chai, sinon and setup.js
- Add snapshot test to ApplicationHeader spec and remove skip nav link
test
- Add an update snapshot test that can be run if a page changes and the
snapshot needs to be updated
- Remove tight coupling of application structure and test in
ApplicationHeader spec

We are changing to Jest for a few reasons:
1. Jest is the testing framework used by most Vue applications and
has robust documentation
2. It requires less configuration and works out of the box
3. It includes the ability to perform snapshot testing of rendered
UI, which is much easier to maintain than trying to test specific UI
elements.

Signed-off-by: Derick Montague <derick.montague@ibm.com>
Change-Id: I7bca3613991ebae1fd464fa3a60f079d044ed7b4
diff --git a/.eslintrc.js b/.eslintrc.js
index d0344ab..02167f4 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -29,7 +29,7 @@
         '**/tests/unit/**/*.spec.{j,t}s?(x)'
       ],
       env: {
-        mocha: true
+        jest: true
       }
     }
   ]