Rename placement methods to fix objc issues

[jjochen]

fixes #111

[codecov]

Codecov Report

Merging #112 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #112   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          11     11           
  Lines         792    792           
  Branches       25     25           
=====================================
  Hits          792    792

Impacted Files	Coverage Δ
Sources/JJFloatingActionButton.swift	100% <100%> (ø)	⬆️
Sources/JJFloatingActionButton+Placement.swift	100% <100%> (ø)	⬆️

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