Merge pull request #516 from dmaclach/master

Fixed -Wundef warnings
Add 1.2.1 changelog.
Version bump to 1.2.1.
[docs] Dafuq. Replace typographic quotation with regular quote in the Doxyfile.
Fix up some CGFloat handling in NIAttributedLabel
Make UIResponder+NimbusCore.h import UIKit.h so that clients don't have to rely on importing it via PCH.
Import UIKit.h in NIActions.m because it references UIKit classes
Import UIKit.h in NIOverviewLogger.h because it references UIKit types
Merge pull request #517 from jverkoey/assorted-fixes

Miscellaneous header import and CGFloat fixes.
[models] Add a unit test to validate proper NITitleCellObject and NISubtitleCellObject subclass initialization.
Merge pull request #518 from jverkoey/new-models-test

[models] Add a unit test to models to validate subclassed cell object initialization
[attributedlabel] Safety checks before calling CFRelease.

Closes #521.
Synthesize reuseIdentifier in the Catalog sample app to avoid crashes.

Closes #522.
Update DONORS.
Update type declarations for AFNetworking usage.
Merge pull request #525 from jverkoey/afnetworking

Update some type declarations for AFNetworking usage.
Allow subclasses to override cache key and background tag for cell background images, since we allow them to override imageForFirst:last:highlighted:drawDivider:. This way the caching facility of imageForFirst:last:highlighted:drawDivider: can be used by subclasses that override that method but call super.
Merge pull request #528 from darrenw/CellBackground

Allow NICellbackground subclasses to override cache key and background tag for cell backgrounds.
[networkimage] Suppress warning about formatting values to strings.
[networkimage] Implement basic maxAge support again.

Closes #286.