Remove AndThen, as StateT was fixed in Cats 1.1

[alexandru]

I fixed IndexedStateT in Cats 1.1 to be stack safe on left-associated binds, or otherwise it was failing the laws of Sync. See: typelevel/cats#2187

But before that we merged that same fix in cats-effect as well, to make a 0.10 release possible. Granted we could have used better synchronization with the Cats 1.1 release, but doesn't matter much.

So now I'm removing my fixes on Sync[StateT[F, S, ?]] from cats-effect as these are no longer necessary, being moved in Cats proper.

Spring cleanup. Although you should see Bucharest right now, it's anything but Spring here 🌨❄️⛄️

[codecov-io]

Codecov Report

Merging #171 into master will decrease coverage by 0.49%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #171     +/-   ##
=========================================
- Coverage   90.01%   89.52%   -0.5%     
=========================================
  Files          47       46      -1     
  Lines        1002      964     -38     
  Branches       78       74      -4     
=========================================
- Hits          902      863     -39     
- Misses        100      101      +1