update artist, genre, song, and spec files based on partA
add app.rb file and isolate strings for name, artist, and genre for each song
correct variable names reflect aspects of song (title, artist, genre)
create song, artist, and genre objects for each song
move isolating name, artist, and genre into separate functions
break method up into smaller methods
correct artist_exist? and genre_exist? methods
refactor create_genre and create_artist methods to accommodate repeating genres and artists
link artists, songs, and genre objects