Added Spleeter support

[gulnazaki]

Spleeter is a source separation library by Deezer, with amazing results. I added it as an option because after hearing MaD Twinnet's output I wasn't that satisfied. But, even though vocals now are much more clear the results have not improved, at least for the songs I tried it to.

To play around add --spleeter as an argument to playback.py

[pep8speaks]

Hello @tom-melistas! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file autosynch/playback.py:

Line 47:80: E501 line too long (121 > 79 characters)
Line 48:80: E501 line too long (171 > 79 characters)
Line 51:80: E501 line too long (123 > 79 characters)
Line 125:80: E501 line too long (92 > 79 characters)

[codecov]

Codecov Report

Merging #34 into master will decrease coverage by 0.40%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master      #34      +/-   ##
==========================================
- Coverage   76.36%   75.95%   -0.41%     
==========================================
  Files          22       22              
  Lines        1117     1123       +6     
==========================================
  Hits          853      853              
- Misses        264      270       +6     

Impacted Files	Coverage Δ
autosynch/playback.py	0.00% <0.00%> (ø)

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