Library view animation glitching (fixes #34)
- Created new parent class for all the LibaryView row views
- In this parent class, setLayerContentsRedrawPolicy to
  NSViewLayerContentsRedrawOnSetNeedsDisplay. This (I believe) means the
  row views do not get redrawn during a resize.

Theory: it was trying to re-drawRect during animation (why I don't know
        because the glitching rows were not being resized) and either
        lagging or screwing up. This prevents that maybe?

Rows still seem to correct after a resize, which is good.