Adds Rails root to the load path in production

In order to keep using explicit requires in SectorPresenter, we need to
add the Rails root to the load path.

The decision to use explicit requires, instead of relying on Rails implicit
loading, was to enable fast unit testing
Undo accidental whitespace removal.
Merge pull request #4 from alphagov/fix-sector-presenter

Adds Rails root to the load path in production