Drop support for Scala 2.10

[fthomas]

No description provided.

[codecov]

Codecov Report

Merging #474 into master will increase coverage by 0.44%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #474      +/-   ##
==========================================
+ Coverage   98.07%   98.51%   +0.44%     
==========================================
  Files          60       57       -3     
  Lines         675      673       -2     
  Branches       12       11       -1     
==========================================
+ Hits          662      663       +1     
+ Misses         13       10       -3

Impacted Files	Coverage Δ
...n/scala/eu/timepit/refined/macros/MacroUtils.scala	100% <ø> (ø)	⬆️
.../scala/eu/timepit/refined/macros/RefineMacro.scala	100% <ø> (ø)	⬆️
...la/eu/timepit/refined/macros/LiteralMatchers.scala	87.5% <ø> (ø)	⬆️
...rc/main/scala/eu/timepit/refined/api/Refined.scala	100% <ø> (ø)

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[fthomas]

From the list of external modules, these are still available for 2.10:

• argonaut-refined
• atto-refined
• ciris-refined
• monocle-refined
• scala-xml-names

Dropping 2.10 support would make it harder for those downstream projects to update refined, so I'll defer this for now.

[fthomas]

Ciris dropped 2.10 support (vlovgr/ciris#161) and Monocle is also considering dropping 2.10 support (optics-dev/Monocle#575 (comment)). I think we can do this now after the 0.9.1 release.