Update app-misc/beersmith/beersmith-2.1.02.ebuild

1. Replaced header version using `s/2012/2013/`.
2. Switched to EAPI 5 which has became stable.
3. Reuse of `MY_PN` by changing `BeerSmith2` to `BeerSmith`.
4. Added `unpacker` eclass, removed `src_unpack`.
5. Added `-*` to keywords, optional though...
6. Sorted dependencies.
7. Changed src_install to not require `cd`, use bash expansion.