The reverse ~ combinator

[sergei-shabanau]

Restored the reverse (~) combinator and added tests.

There is a build.sbt update here that

1. bumps scalaz-base version to around mid-september snapshot.
2. adds possibility to work will universally quantified functions that are used for natural transformation encoding in v.8. This is also PRed to scalaz-sbt plugin here Added "-Xsource:2.13" compiler option scalaz/scalaz-sbt#22

[codecov-io]

Codecov Report

Merging #12 into master will increase coverage by 7.44%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #12      +/-   ##
==========================================
+ Coverage    5.71%   13.15%   +7.44%     
==========================================
  Files           1        1              
  Lines          35       38       +3     
==========================================
+ Hits            2        5       +3     
  Misses         33       33

Impacted Files	Coverage Δ
src/main/scala/scalaz/parsers/Iso.scala	13.15% <100%> (+7.44%)	⬆️

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[ryanonsrc]

May consider converting to ScalaCheck later, but for now: LGTM