Make the redirect to /api a permanent redirect
Tidy up routing for jobsearch and add an integration test

We might be able to move the redirect for api requests out of the controller
but we should make sure we have a test for the current behaviour before
doing that.
Move API redirect for jobsearch to the routes file

Doing the redirect further up will be more efficient and simplifies the
RootController#jobsearch method
Remove old functional test for jobsearch api redirects

This happens in routes.rb now which isn't tested in functional tests.
The new integration test will do the same job.
Merge pull request #287 from alphagov/refactor-jobsearch

Move jobsearch API redirect to routes file