Change deployement target to 4.x as NSCache wasn't available in 3.0

SDWebImage.xcodeproj/project.pbxproj

@@ -581,7 +581,7 @@
 				GCC_WARN_UNUSED_LABEL = YES;
 				GCC_WARN_UNUSED_PARAMETER = NO;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 3.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 4.3;
 				PUBLIC_HEADERS_FOLDER_PATH = include/SDWebImage;
 				RUN_CLANG_STATIC_ANALYZER = YES;
 				SDKROOT = iphoneos;
@@ -608,7 +608,7 @@
 				GCC_WARN_UNUSED_LABEL = YES;
 				GCC_WARN_UNUSED_PARAMETER = NO;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 3.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 4.3;
 				PUBLIC_HEADERS_FOLDER_PATH = include/SDWebImage;
 				RUN_CLANG_STATIC_ANALYZER = YES;
 				SDKROOT = iphoneos;