Remove layout provider classes

[mac-gallagher]

• Remove LayoutProvider classes to simplify implementation
• Add SwiftLint checks to ShuffleTests and ShuffleExample targets
• Add Pods/ directory to .gitignore
• Remove swipe/reverse swipe completion blocks in favor of calling directly in completion
• Make code coverage checks non-blocking for PRs

[codecov-io]

Codecov Report

Merging #137 (41293ce) into master (90adc0e) will decrease coverage by 0.7%.
The diff coverage is n/a.

❗ Current head 41293ce differs from pull request most recent head ccda241. Consider uploading reports for the commit ccda241 to get more accurate results

@@           Coverage Diff            @@
##           master    #137     +/-   ##
========================================
- Coverage    84.8%   84.1%   -0.8%     
========================================
  Files          13      11      -2     
  Lines         759     724     -35     
========================================
- Hits          644     609     -35     
  Misses        115     115             

Impacted Files	Coverage Δ
...urces/Shuffle/Classes/SwipeCard/CardAnimator.swift	100.0% <ø> (ø)
Sources/Shuffle/Classes/SwipeCard/SwipeCard.swift	100.0% <ø> (ø)
Sources/Shuffle/Classes/SwipeCard/SwipeView.swift	100.0% <ø> (ø)
...ses/SwipeCardStack/CardStackAnimationOptions.swift	100.0% <ø> (ø)
...fle/Classes/SwipeCardStack/CardStackAnimator.swift	0.0% <ø> (ø)
...Classes/SwipeCardStack/CardStackStateManager.swift	100.0% <ø> (ø)
...huffle/Classes/SwipeCardStack/SwipeCardStack.swift	100.0% <ø> (ø)