Don't expose context to extract_params method
Flatten aspect/service composition

+@evilstreak
Merge pull request #28 from alphagov/flatten-service-pyramid

Flatten service pyramid
Make db:setup a proper rake task

Move it into a `.rake` file and give it a description so it shows up in
`rake -T`.
Add db:migrate rake task

For consistency with all the other apps, add a rake task to run database
migrations which can be run as part of deploys.

Log all output to STDOUT so it can be seen in the deploy logs in
Jenkins.
Remove host and user from postgres config

Access to a local postgres database on the development VM is done
through a socket, which doesn't use host, username nor password.

This is a repeat of eb53232 which was accidentally blatted in a rebase by
3793cdc.
Remove obsolete migrate script

We have a db:migrate rake task so this isn't needed any more.