5.0.0

This release accomplishes two goals.

1. The RequestBuilder type is no longer opaque. This comes after observing
   much debate in the community over the merits and drawbacks of hiding details of
   a library's types from the user. In this case I have determined it no longer
   makes sense to do so. If RequestBuilder is opaque and so is Http.Request,
   there is no longer any opportunity to do introspection, write tests, or create
   tooling around the RequestBuilder type. So we simply expose the internal
   structure of RequestBuilder as a record.
2. We're taking over the send function again. Thanks to a pull request by @s60
   I am convinced that this will be okay. We can still have the same signature for
   send, and then use tasks inside of send to mess around and do extra stuff.
   This will just require that the docs for toRequest be very clear that it is
   lossy with respect to HttpBuilder features. So far there is one new feature
   that is being brought over from the previous versions, withCacheBuster. This
   will be a foundation for bringing back other stuff and adding new things as
   well.

Removals

None

Breaking Changes

• RequestBuilder a is no longer opaque

Additions

• toTask: Convert your RequestBuilder a into a Task Http.Error a with all
  the extras that HttpBuilder has and will have to offer.
• withCacheBuster: append a cache buster query param with the current
  timestamp to your request's URL.