Use scalameta scalafmt plugin

[regadas]

As I expected the switch to the official and updated scalafmt introduces a "some" changes. sbt files are also being checked now.

[regadas]

So apparently, I think there's an issue with mima and scala 2.12.10; The issue is visible in this job and the in the previous commit merged to master.

lightbend-labs/mima#387

[johnynek]

I think we should stay on 2.12.8 or 9 rather than introduce binary incompatibilities.

[regadas]

@johnynek I went through 2.12.{8, 9, 10} and MiMa reports issues in all of them when comparing against the latest version 0.13.5 with 2.12.7. AFAICT it's mostly the DirectMissingMethodProblem which, and if i understood correctly, is related to what @dwijnand mentioned.

Since this is a new thing being reported and previous kinda have the same issue, maybe it's kind of ok to exclude this for now till a new release is out?

[dwijnand]

I've opened lightbend-labs/mima#388 that describes the problem and how MiMa could be enhanced to handle it universally.

[codecov-io]

Codecov Report

Merging #681 into develop will increase coverage by 0.15%.
The diff coverage is 77.77%.

@@             Coverage Diff             @@
##           develop     #681      +/-   ##
===========================================
+ Coverage     89.5%   89.65%   +0.15%     
===========================================
  Files          112      112              
  Lines         8943     8944       +1     
  Branches       314      314              
===========================================
+ Hits          8004     8019      +15     
+ Misses         939      925      -14

Impacted Files	Coverage Δ
...re/src/main/scala/com/twitter/algebird/QTree.scala	79.41% <ø> (ø)	⬆️
...la/com/twitter/algebird/monad/StateWithError.scala	42.1% <ø> (ø)	⬆️
...in/scala/com/twitter/algebird/BaseProperties.scala	97.61% <ø> (ø)	⬆️
...src/main/scala/com/twitter/algebird/Preparer.scala	29.03% <ø> (ø)	⬆️
...com/twitter/algebird/GeneratedProductAlgebra.scala	97.43% <ø> (ø)	⬆️
...src/main/scala/com/twitter/algebird/Identity.scala	66.66% <ø> (ø)	⬆️
...witter/algebird/bijection/AlgebirdBijections.scala	0% <ø> (ø)	⬆️
...main/scala/com/twitter/algebird/RightFolded2.scala	94.44% <ø> (ø)	⬆️
...gebird/util/summer/HeavyHittersCachingSummer.scala	86.9% <ø> (ø)	⬆️
.../com/twitter/algebird/util/summer/NullSummer.scala	88.88% <ø> (ø)	⬆️
... and 43 more

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[regadas]

@johnynek rebased with develop

[johnynek]

Thanks!