Make animation options structs instead of classes

[mac-gallagher]

Previously, changing animation options would have to be done via creating a new CardAnimationOptions object and setting the card's animationOptions property. Now, one can modify the animation properties directly, e.g. card.animationOptions.totalSwipeDuration = 2.0

Additionally:

• Removed animation options unit tests as they do not provide much use
• Update all animation durations to have minimum value CGFloat.leastNormalMagnitude
• Cleaned up some of the animation code and removed some animation tests that did not provide much value

[codecov-io]

Codecov Report

Merging #142 (35a3957) into master (7b746c2) will decrease coverage by 2.3%. The diff coverage is 36.9%.

@@           Coverage Diff            @@
##           master    #142     +/-   ##
========================================
- Coverage    84.0%   81.7%   -2.4%     
========================================
  Files           9       9             
  Lines         707     700      -7     
========================================
- Hits          594     572     -22     
- Misses        113     128     +15     

Impacted Files	Coverage Δ
...ses/SwipeCardStack/CardStackAnimationOptions.swift	0.0% <0.0%> (-100.0%)	:arrow_down:
...fle/Classes/SwipeCardStack/CardStackAnimator.swift	0.0% <0.0%> (ø)
...uffle/Classes/SwipeCard/CardAnimationOptions.swift	33.3% <33.3%> (-66.7%)	:arrow_down:
...urces/Shuffle/Classes/SwipeCard/CardAnimator.swift	100.0% <100.0%> (ø)
Sources/Shuffle/Classes/SwipeCard/SwipeCard.swift	100.0% <100.0%> (ø)
...huffle/Classes/SwipeCardStack/SwipeCardStack.swift	95.3% <100.0%> (ø)