Added separateFoldable

[tkroman]

#2741

Since this is a new method, mima is breaking but I haven't used it before, so not sure what to do here.

[codecov-io]

Codecov Report

Merging #2742 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #2742      +/-   ##
==========================================
+ Coverage   93.28%   93.28%   +<.01%     
==========================================
  Files         376      376              
  Lines        7323     7328       +5     
  Branches      174      205      +31     
==========================================
+ Hits         6831     6836       +5     
  Misses        492      492

Flag	Coverage Δ
#scala_version_212	93.62% <100%> (ø)	⬆️
#scala_version_213	90.92% <80%> (-0.03%)	⬇️

Impacted Files	Coverage Δ
core/src/main/scala/cats/Alternative.scala	92.3% <100%> (+3.41%)	⬆️
core/src/main/scala/cats/syntax/alternative.scala	100% <100%> (ø)	⬆️

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[kailuowang]

Thanks for the contribution. There is ways to get around breaking binary compatibility for this type of addition, but there are quite some hoops to jump through. The good news is in Q2 we are going to allow this type of changes on master with a new branching scheme. So if you can wait, it might be easier to just schedule this to cats 2.1. Otherwise I can guide you on how to avoid breaking BC on Scala 2.11. Let me know.

[tkroman]

@kailuowang I can definitely wait, but I'm OK with jumping through the hoops as well, so I defer to your judgement.

[kailuowang]

If you can wait, let's wait to avoid the extra boilerplate code on master.

[travisbrown]

@tkroman Do you mind merging master to fix the build? Otherwise looks good to me.

[travisbrown]

I think we should drop SeparateFoldableOps but otherwise looks good to me.

[travisbrown]

@tkroman Thanks! I think it'll still need merging with master to avoid the 2.11 bincompat check.

[travisbrown]

CI failure was Travis nonsense, just restarted that job.

[tkroman]

woohoo, thanks!