Missing functionality in genres.erb and genre_show.erb

genres.erb should be sorted by song-count. genre_show.erb should include
the total unique artists and song counts in the genre. genre.erb and artists.erb have unnecessary 'i' variable in #each pipes.
Merge branch 'comments-ivanbrennan' of github.com:loganhasson/playlister-rb-unit-1 into comments-ivanbrennan