Remove BeautifulSoup dependency (as of #191)

requirements.txt

@@ -1,9 +1,8 @@
 pathlib >= 1.0.1
-BeautifulSoup4 >= 0.4.13
 youtube_dl >= 2017.5.1
 pafy >= 0.5.3.1
 spotipy >= 2.4.4
 mutagen >= 1.37
 unicode-slugify >= 0.1.3
 titlecase >= 0.10.0
-logzero >= 1.3.1
+logzero >= 1.3.1

spotdl.py

@@ -5,7 +5,6 @@ from core import logger
 from core import metadata
 from core import convert
 from core import internals
-from bs4 import BeautifulSoup
 from titlecase import titlecase
 from slugify import slugify
 import spotipy