Migrate JS tests to Jest and update libraries (#74)

- Move from Mocha to Jest for JS testing (Jest seems to have better support for
 'watching' tests and a more active community these days).
- Codemod existing tests to Jest syntax (using https://github.com/skovhus/jest-codemods)
- Fix some errors in tests that were previously hidden.
- Update Babel.

frontend/components/forms/validators/validate_query/validate_query.tests.js

@@ -1,5 +1,3 @@
-import expect from 'expect';
-
 import validateQuery from './index';
 
 const malformedQueries = [
@@ -42,7 +40,7 @@ describe('validateQuery', () => {
     validQueries.forEach((query) => {
       const { error, valid } = validateQuery(query);
       expect(valid).toEqual(true, query);
-      expect(error).toNotExist();
+      expect(error).toBeFalsy();
     });
   });
 });