Merge pull request #232 from alexanderedge/master

Cells are not added in the same order as layoutAttributesArray
Fixes an issue where cells weren't being drawn

	- When the bounds were being updated frequently removing old cells first would sometimes result in the superview of a visible view being nil. Adding new cells first prevents this and allows us to optimize the creation of the allVisibleItemKeys set by only iterating over _allVisibleViewsDict once.
Merge pull request #233 from 500px/Issue#226-Dissappearing-cells

Issue #226 -  Fixes an issue where cells weren't being drawn
Cells Missing after updateVisibleCellsNow

	In some cases where the cells are sufficiently large and `showsHorizontalScrollIndicator` and `showsVerticalScrollIndicator` are both `NO` the number of subviews becomes zero. If this happens and `self.dragging` is `YES` then we are trying to insert the cell at a negative index which will not add the subview. Any subsequent insertion will also fail since the number of subviews will still be zero. This fix ensures that we insert the cell at a non-negative index.
Adds inline documentation to fix and cleans it up a bit
Merge pull request #235 from 500px/Missing-Cells-take-two

Fixes issue where Cells are Missing after updateVisibleCellsNow
some explanation in comments added
Merge pull request #239 from gavrix/bugfix

some explanation in comments added
Modify highlighting behavior when cell's setHighlighted method is not overwritten - specifically touchesMoved behavior
Adjust some typos in some in-line comments.
Merge pull request #240 from educreations/fix-typos

Adjust some typos in some in-line comments.
A test case to reproduce an animation bug.
Add pedantic touching state cleaning
added support for the collection view cell's [will/did]TransitionFromLayout:toLayout:
Merge pull request #245 from taiyangc/select_background

Modify highlighting behavior when cell's setHighlighted method is not ov...
Add some documentation
Code style
Fix stack overflow caused during scroll view delegate callbacks
Document delegate setting
mostly code style improvements