Use NSCache instead of a dictionary for the memory cache.
Podspec: Add 'MK' as acceptable prefix for MKAnnotationView category
Keeping original image alpha info when decoding

This fixes issue #26 and #55, after the change introduced in commit c32f9c03f816dac58a8cac25d6189310272ca9c1
Creating the CGBitmapContext with the right bytes per pixel and bitmap info depending on the original image.
This removes an error that was making CGBitmapContext return NULL with some images:
<Error>: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; kCGImageAlphaLast; 400 bytes/row.
Switch to framework distribution
Add missing installation instruction about linker flag
Fix #200 crash on archived builds
Fixed Alpha chanel detection when decoding images.
Send downloader as part of notification.
Add NSCache's cost argument
Fix example app
Change deployement target to 4.x as NSCache wasn't available in 3.0
Revert "Fixed Alpha chanel detection when decoding images."

This reverts commit e6ede1104cea39f2034ec5a1644e2d2082cc57bd.
Fixed Alpha chanel detection when decoding images.
Fix alpha handling in image decoder (fix #204)
Add cancelAll method (fix #168)
First beta of SDWebImage 3.0

This version is a rewrite of the lib using iOS 5.0 as minimum target.
The lib as thus been refactored to use blocks/GCD from the ground up.
As a consequence, all delegate code style has been removed. The result
is a lot less lines of code and more flexibility.
Add who use it section
Remove outdated motivation section
Add "How is SDWebImage better than X?" wiki link