Adds PSTCollectionView

Using the PSTCollectionView.podspec available in the repo.
Somehow the author do not submits the spec to the specs repo
thus this PR from me.

PSTCollectionView/0.0.1/PSTCollectionView.podspec

@@ -0,0 +1,20 @@
+Pod::Spec.new do |s|
+  s.name = 'PSTCollectionView'
+  s.version = '0.0.1'
+  s.summary = 'Open Source, 100% API compatible replacement of UICollectionView for iOS4+.'
+  s.homepage = 'https://github.com/steipete/PSTCollectionView'
+  s.license = {
+    :type => 'MIT',
+    :file => 'LICENSE'
+  }
+  s.author = 'Peter Steinberger', 'steipete@gmail.com'
+  s.source = {
+    :git => 'https://github.com/steipete/PSTCollectionView.git',
+    :commit => 'HEAD'
+  }
+  s.platform = :ios, '4.3'
+  s.source_files = 'PSTCollectionView/'
+  s.public_header_files = 'PSTCollectionView/'
+  s.frameworks = 'UIKit', 'QuartzCore'
+  s.requires_arc = true
+end