test: add initial jest tests

Basic jest tests are added for the landing page. These tests use the
react testing library so the enzyme dependencies are removed from the
package.json. The travis config is also updated.

src/SmartComponents/LandingPage/CreateImageCard.js

@@ -20,7 +20,7 @@ class CreateImageCard extends Component {
 
     render() {
         return (
-            <Card>
+            <Card data-testid="create-image-card">
                 <CardHeader>Create a new image</CardHeader>
                 <CardBody>
                     <Form>