Change default minimum OS version to 8.0

Although iOS 7 is supported in the source code, package managers (CocoaPods and Carthage) build a Swift dynamic framework, which is only supported on iOS 8.0 and later. Therefore we switch the minimum OS version to 8.0 in the project. (Fixes #75.)

Author: Clément Le Provost

AlgoliaSearch.xcodeproj/project.pbxproj

@@ -656,7 +656,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 7.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 8.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				MTL_ENABLE_DEBUG_INFO = YES;
 				ONLY_ACTIVE_ARCH = YES;
@@ -697,7 +697,7 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 7.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 8.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				SDKROOT = macosx;