Merge pull request #575 from LiyeZhang/master

Adding a simple description implementation to NICollectionViewModel for debugging
[collections] Add call to super in description.
Fix some warnings where CGFloats were being truncated to floats in a 64-bit build
Merge pull request #576 from zszego/cgfloat_64bit_fixes

Fix some warnings where CGFloats were being truncated to floats in a 64-bit build
[overview] Add missing import to NIOverviewGraphView.
Merge pull request #578 from jverkoey/missing-import

[overview] Add missing import to NIOverviewGraphView.
Merge pull request #2 from jverkoey/master

Merging from upstream