DefaultJws class doesn't propagate the generic B type to the interface

[josebarrueta]

By not propagating the generic type to specific generic to the interface, IDEs warn of not passing the specific type in the Jws.

For example:

 Jws<MyClaims> jws = Jwts.parser().setSigningKeyResolver(issuerSigningKeyResolver).parse(jwt, new JwtHandlerAdapter<Jws<MyClaims>>() {
                @Override
                public Jws<MyClaims> onClaimsJws(Jws<Claims> jws) {
                    MyClaims myClaims = ...;
                    return new DefaultJws<>(jws.getHeader(), myClaims, jws.getSignature());
                }
            });

The IDE complains the the returned type is not of Jws<MyClaims>.

Solution will be add the generic body to the signature of the class:

public class DefaultJws<B> implements Jws<B>

[lhazlewood]

Resolved by PR #40. Will be released in 0.6.