web: expose raw request function in API
web: expose raw request function in API

This will be useful for performing requests that don't conform to the
regular patterns. For instance, `/sky/logout` is a GET request that does
not return JSON.

Signed-off-by: Aidan Oldershaw <30ef7a6e0d016bc846f26d89dacbd23aceded206@pivotal.io>

concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse,concourse/concourse