* Remove old code
* Rewrite with tests
This implements a fassade pattern for ref library
With the fassade, we can specify the hasher in a rather easy way, which
is not possible with default generics for traits.
The "default" part in "default generic type" is not properly implemented
yet (as visible in the tests), as I don't know how to realize this.
For simplicity, the `hasher` module exports a `default` module with a
`DefaultHasher` type, which resolves to the `Sha1Hasher`.
Signed-off-by: Matthias Beyer <mail@beyermatthias.de>
