stop using aliased parameters, to fix #5

Since 2013-10-10, t/app/rssfilter/group/group.t has been failing due to
```
Can't located Data/Alias in @INC (@INC contains: ... ) at /home/dgh/.perlbrew/libs/perl-5.16.1/lib/perl5/Method/Signatures.pm line 1121
```

Release 20131010 of Method::Signatures changed Data::Alias from a prerequisite to a recommended, and thus consumers should require it themselves.

I've removed the reliance on aliased parameters which causes M::S to require D::A.