CHANGELOG: Add with a note on 1.0.0

Release 0.2.0: Fix configuration issues

`etag_plug` wrongly assumed that the default configuration would be
copied over from the lib. It now changed it's configuration paradigm to
use hardcoded defaults if no configuration has been passed in.

Release 0.1.0 - Functional shallow ETag plug:

This release allows you to use the `ETag.Plug` which simply generates a
shallow etag on the `resp_body` of a `Plug.Conn` it takes care of
comparing it against the header value in `if-none-matches` and sends a
304 response if it matches.