As mentioned in the previous commit, `<Main>` doesn't really
belong in App.js, it instead belongs in LandingPage.js, because
it creates the html/css wrapper for the main contents, as a
sibling to the `<PageHeader>` component used in LandingPage.js.
However, including `<Main>` in LandingPage.js will cause the
tests to fail. Therefore, just the html and classes that
`<Main>` creates is used in LandingPage.js.
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.
The Main component in the LandingPage component has been moved to the
App component. This is required so the tests can mock the store without
any insights information.
