Adding dequeue from Nib

Adding methods to dequeue cells and supplementary views from Nib, in addition to classes.
Adding property to enable/disable item padding in grid layout

New property to enable / disable even horizontal padding between items in grid layout.
Review changes
Merge pull request #95 from kettch/master

Adding dequeue from Nib
Merge pull request #99 from jwilling/override-init-layout

Fix layout initializers
allow the layout to change scroll direction
Merge pull request #101 from jwilling/scroll-direction

Add preliminary scroll direction support
Adding property to enable/disable item padding in grid layout
Merge pull request #98 from kettch/disable-padding

Adding property to enable/disable item padding in grid layout
upgrade project files for Xcode 5.1
fix a bug where the document size didn't equal the bounds

A common source for this occurred when legacy scrollers were enabled.
The bounds for the collection view would remain the same, but the
usable area of the scroll view (the document visible rect) would
change. To fix this, we now check the document visible rect’s size
instead of the bounds when determining if the collection view needs a
redraw.
Merge pull request #104 from jwilling/upgrade-projects

Upgrade project files for Xcode 5.1
Merge pull request #105 from jwilling/fix-legacy-scrollers

Fix a bug where the document size didn't equal the bounds
fix issue where data was referencing frame instead of doc size

Caused the content to be scrollable horizontally when legacy scrollbars
were enabled.
Merge pull request #106 from jwilling/fix-incorrect-data-size

Fix incorrect content size
switch to C array of section data for performance reasons

Seems to result in a massive boost in performance when there are a
large number of sections.
Merge branch 'master' into performance-improvements
documentation and header cleanup for data class