Fix XCode 10.2 warnings

[MontakOleg]

'public' modifier is redundant for instance method declared in a public extension

[lucdion]

Thanks for the contribution 👍

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@6860823). Click here to learn what that means.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master     #193   +/-   ##
=========================================
  Coverage          ?   93.07%           
=========================================
  Files             ?       44           
  Lines             ?     8969           
  Branches          ?        0           
=========================================
  Hits              ?     8348           
  Misses            ?      621           
  Partials          ?        0

Impacted Files	Coverage Δ
Sources/Extensions/PEdgeInsets+Operators.swift	0% <0%> (ø)

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[lucdion]

Release 1.8.8 available
https://github.com/layoutBox/PinLayout/releases/tag/1.8.8