Fixes deleting sections.

Signed-off-by: Daniel Thorpe <daniel.thorpe@corp.badoo.com>
Merge pull request #156 from danthorpe/delete_sections

Fixes deleting sections.
Applied LayoutAttributes to Cell/SupplementaryView at dequeue time as opposed to configuration time.
Optimised images
Merge pull request #155 from pinterest/Layout_Attribute_Application_Fix

Cell LayoutAttributes Should be Applied Before "cellForItemAtIndexPath:"
Merge pull request #159 from imageoptimiser/optimised-images

Optimise images (1 MB reduction)
fixes a typo
Honor the z-index of PSTCollectionReusableView's when adding them to the PSTCollectionView
Merge pull request #160 from pinterest/aly_view_ordering

Honor the z-index of PSTCollectionReusableView's when adding as subviews to PSTCollectionView
Inserting cells without initialLayoutAttrs bugfix

(now using regular layoutAttrs with fade-in using alpha)
Merge pull request #164 from gavrix/bugfix

Inserting cells without initialLayoutAttrs bugfix
Added the UIView designated initializer
Merge pull request #165 from smule/master

Override the UIView designated initializer in PSTCollectionView
Fix highlighting behavior and reorganize how selection and highlighting iteract
fix incompatible pointer type warning for Deployment Targets >= iOS 6.0
Merge pull request #169 from mikevoyt/fixwarnings

fix incompatible pointer type warning for Deployment Targets >= iOS 6.0
Merge pull request #166 from taiyangc/highlight

Fix highlighting behavior and reorganize how selection and highlighting ...
Update header
- fix targetContentOffsetForProposedContentOffset:withScrollingVelocity: not called
- relay UIScrollViewDelegate methods to _collectionViewDelegate