[WM WR] allow restricted request body types in body-params

This is a breaking change for users of the library, so we should bump the
minor version number before releasing. Specifically,
`turbovote.pedestal-toolbox.params/body-params` used to be a before
interceptor itself. Now it's a fn that generates a before interceptor.

So all occurrences of `body-params` in consuming code will need to become
`(body-params)`. On the plus side, this more closely mirrors the upstream
version it's overriding.

If a request has a body type that isn't allowed or parseable, this will now
respond with a 415 Unsupported Media Type.
[WM] bump minor version number in project.clj

The API has changed.
`body-params` is now an interceptorfn, so call `(body-params)` instead.
[WM] remove backwards-compatibility alias and document API changes in CHANGELOG.md
[WM] make the intent of mocked requests w/ accept headers clearer in tests

Trying to avoid the inevitable confusion over Content-Type vs. Accept.
[WM] clarify that route tables can handle interceptorfns on their own
Merge pull request #11 from turbovote/stricter-body-params

[WM WR] allow restricted request body types in body-params