Backport minimum/maximum/ByOption from Foldable to scala_2.11

[gagandeepkalra]

addresses #3143

[codecov-io]

Codecov Report

Merging #3297 into scala_2.11 will increase coverage by <.01%.
The diff coverage is 100%.

@@              Coverage Diff               @@
##           scala_2.11    #3297      +/-   ##
==============================================
+ Coverage       93.45%   93.46%   +<.01%     
==============================================
  Files             384      384              
  Lines            7155     7159       +4     
  Branches          198      197       -1     
==============================================
+ Hits             6687     6691       +4     
  Misses            468      468

Impacted Files	Coverage Δ
core/src/main/scala/cats/syntax/reducible.scala	100% <100%> (ø)	⬆️
core/src/main/scala/cats/syntax/foldable.scala	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e37485f...28a1827. Read the comment docs.