fix duplicate symbols when using with webp via pods
Refactor the cancel logic
Merge branch 'master' into new_cancel_logic

Conflicts:
	SDWebImage/MKAnnotationView+WebCache.m
	SDWebImage/UIButton+WebCache.m
	SDWebImage/UIImageView+HighlightedWebCache.h
	SDWebImage/UIImageView+HighlightedWebCache.m
	SDWebImage/UIImageView+WebCache.m
Prepared gitignore for CocoaPods and workspaces
Created a SDWebImage workspace with the 2 existing projects, fixed the demo project so it directly references the source files. Shared a demo project scheme
Added SDWebImage Tests project. It uses CocoaPods (Expecta + XCTestAsync). Added some demo tests
Added error test
Reverted demo project referencing source files directly. Re-added SDWebImage project as subproject
Merge branch 'unit_tests'

Unit testing setup + created workspace
- created a SDWebImage.xcworkspace
- includes the existing SDWebImage.xcodeproj (responsible of compiling the library)
- includes the existing SDWebImage Demo.xcodeproj
- includes the newly created SDWebImage Tests.xcodeproj (tests project). The test project uses the local CocoaPods repo to link to the library

Unit testing backbone:
- XCTest framework (the one from Apple)
- XCTestAsync - extension for XCTest that allows easily creating asynchronous tests. Relies on dispatch_after.
- Expecta - matcher Framework for Objective-C/Cocoa

Updated gitignore
Implemented NTLM auth support. Replaced deprecated auth challenge methods from `NSURLConnectionDelegate`. Replaces #711.
- added `username` and `password` properties on `SDWebImageDownloader`
- added `shouldUseCredentialStorage` and `credential` properties on `SDWebImageDownloaderOperation`
- `SDWebImageDownloaderOperation` conforms to `NSURLConnectionDataDelegate` (it used to implement the methods, but didn't stated the protocol in the declaration)
- removed deprecated methods: `- connection:canAuthenticateAgainstProtectionSpace:` and `- connection:didReceiveAuthenticationChallenge:` with `- connectionShouldUseCredentialStorage:` and `- connection:willSendRequestForAuthenticationChallenge:`
- updated demo project to download one image the requires HTTP auth
Do not load placeholder image if SDWebImageDelayPlaceholder option specified.
Merge pull request #780 from rokgregoric/master

Do not load placeholder image if SDWebImageDelayPlaceholder option specified.
Merge pull request #771 from Whirlwind/new_cancel_logic

Refactor the cancel logic
Added comments and coding style to previous pull request #771
Update for #771 - instead of removing the old methods, deprecated them so we are backwards compatible.
Fixed #775, made sure all the category methods that are public have the sd_ prefix (deprecated the old ones)
-there were a few exceptions where I just renamed the methods since they were added in this method
Added option to use the cached image instead of the placeholder for UIImageView. Replaces #541. Fixes #599
Replace #621Fixed race condition between operation cancelation and loading finish
Fixed misspell
Updated README.md with badges