add some authors, books, and a user to seeds.rb

They all have the same cover, and there are no isbns, tags, or reviews
add tags to seeds

the tags are not attached to anything yet
Merge branch 'seeds' of github.com:nbirnel/Library-Application into seeds
make tag seeds attach to books

also refactored the seeds a little
Merge pull request #84 from nbirnel/seeds

Seeds