Update 2.11 branch build

[travisbrown]

Backports a couple of @larsrh's changes from #3079 to the scala_2.11 branch.

The CI failure in #3137 isn't what I'd expect (I got a different one with the same changes locally), but I think this should fix it.

[codecov-io]

Codecov Report

Merging #3139 into scala_2.11 will decrease coverage by 0.02%.
The diff coverage is n/a.

@@              Coverage Diff               @@
##           scala_2.11    #3139      +/-   ##
==============================================
- Coverage        93.4%   93.37%   -0.03%     
==============================================
  Files             382      382              
  Lines            7155     7155              
  Branches          195      195              
==============================================
- Hits             6683     6681       -2     
- Misses            472      474       +2

Impacted Files	Coverage Δ
core/src/main/scala/cats/data/Op.scala	77.77% <ø> (ø)	⬆️
...tances/ScalaVersionSpecificParallelInstances.scala	90.9% <ø> (ø)	⬆️
core/src/main/scala/cats/instances/parallel.scala	0% <ø> (ø)	⬆️
core/src/main/scala/cats/instances/sortedSet.scala	88.23% <ø> (ø)	⬆️
core/src/main/scala/cats/instances/sortedMap.scala	84.74% <ø> (ø)	⬆️
testkit/src/main/scala/cats/tests/Helpers.scala	96% <0%> (-4%)	⬇️
...cala/cats/kernel/instances/FunctionInstances.scala	96.96% <0%> (-3.04%)	⬇️

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[travisbrown]

@jackcviers Mind taking a look / signing off on this?