Fix typos detected by github.com/client9/misspell

[seratch]

Fixing typos is sometimes very hard. It's not so easy to visually review them. Recently, I discovered a very useful tool for it, misspell.

This pull request fixes minor typos detected by misspell except for the false positives. If you would like me to work on other files as well, let me know.

before

$ misspell . | grep -v '/target/'
PROCESS.md:90:40: "occured" is a misspelling of "occurred"
CHANGES.md:806:20: "preceeded" is a misspelling of "preceded"
core/src/main/scala/cats/Reducible.scala:95:5: "Overriden" is a misspelling of "Overridden"
core/src/main/scala/cats/Reducible.scala:107:5: "Overriden" is a misspelling of "Overridden"
core/src/main/scala/cats/UnorderedFoldable.scala:47:14: "overriden" is a misspelling of "overridden"
core/src/main/scala/cats/data/AndThen.scala:160:41: "substract" is a misspelling of "subtract"
core/src/main/scala/cats/data/AndThen.scala:161:12: "comparisson" is a misspelling of "comparisons"
core/src/main/scala/cats/evidence/package.scala:31:33: "refered" is a misspelling of "referred"
docs/src/main/tut/datatypes/eithert.md:107:0: "Similary" is a misspelling of "Similarly"
kernel-laws/src/main/scala/cats/kernel/laws/SerializableLaws.scala:26:5: "suport" is a misspelling of "support"
tests/src/test/scala/cats/tests/EvalSuite.scala:23:43: "occuring" is a misspelling of "occurring"
tests/src/test/scala/cats/tests/EvalSuite.scala:151:39: "faciliate" is a misspelling of "facilitate"

after

$ misspell . | grep -v '/target/'
$

[codecov-io]

Codecov Report

Merging #2378 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #2378   +/-   ##
=======================================
  Coverage   95.01%   95.01%           
=======================================
  Files         349      349           
  Lines        5998     5998           
  Branches      222      222           
=======================================
  Hits         5699     5699           
  Misses        299      299

Impacted Files	Coverage Δ
core/src/main/scala/cats/UnorderedFoldable.scala	87.5% <ø> (ø)	⬆️
...main/scala/cats/kernel/laws/SerializableLaws.scala	93.75% <ø> (ø)	⬆️
core/src/main/scala/cats/data/AndThen.scala	94.33% <ø> (ø)	⬆️
core/src/main/scala/cats/Reducible.scala	95.38% <ø> (ø)	⬆️

---

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[LukaJCB]

Great PR, thanks very much :)

[ceedubs]

Nice! Thank you, @seratch.