Add setuptools as a dependency

[luksak]

I am still facing this issue on macOS 10.14.6 when installing banshee:

$ brew install exaile/exaile/exaile
==> Installing exaile from exaile/exaile
==> Downloading https://github.com/exaile/exaile/releases/download/4.0.0/exaile-
Already downloaded: /Users/lukasvonblarer/Library/Caches/Homebrew/downloads/2284b5a946b835f5c4b7727f8f56d82ce4e4d65c825959a61711370e3a7f3b35--exaile-4.0.0.tar.gz
==> Downloading https://files.pythonhosted.org/packages/11/74/2c151a13ef41ab9fb4
Already downloaded: /Users/lukasvonblarer/Library/Caches/Homebrew/downloads/507d2087bf24df82641b681a5fe4da778ef50ebe819a86ea1b584f70788f0f63--virtualenv-16.7.4.tar.gz
==> python -c import setuptools... --no-user-cfg install --prefix=/private/tmp/e
Last 15 lines from /Users/lukasvonblarer/Library/Logs/Homebrew/exaile/01.python:
-c
import setuptools, tokenize
__file__ = 'setup.py'
exec(compile(getattr(tokenize, 'open', open)(__file__).read()
  .replace('\r\n', '\n'), __file__, 'exec'))
--no-user-cfg
install
--prefix=/private/tmp/exaile--homebrew-virtualenv-20191007-61389-ufqtjw/target
--install-scripts=/private/tmp/exaile--homebrew-virtualenv-20191007-61389-ufqtjw/target/bin
--single-version-externally-managed
--record=installed.txt

Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named setuptools

If reporting this issue please do so at (not Homebrew/brew or Homebrew/core):
  https://github.com/exaile/homebrew-exaile/issues