Configure Travis to deploy to Heroku
Add homepage :seedling:
Create header component
Set up shared base layout and basic homepage
Rename partials to components, add html extension
Add title to homepage
Route homepage to the show action
Merge branch 'homepage'
Add error pages.

Similarly to [register_your_interest db75fbcab8](https://github.com/guidance-guarantee-programme/register_your_interest/commit/db75fbcab8654f879b0e17b077067372641e6e4e) by @andrewgarner

Check out the layout of these error pages @aduggin?
Respond with 404 template when an article is not found.

Note: The exceptions_app mechanism used by [Gaffe] is Rack-based. Rails controllers specs do not go through Rack. Request specs do.

[gaffe]: http://open.mirego.com/gaffe/
Avoid using {...} for multi-line blocks.

Rubo :cop:
Use default h1 for error page and update text
Get error pages to use correct layout