Set deployment target to 10.10 for the minimum OS X version for this app

I'm currently using features only available in 10.10 or above.  We'll have to discuss this and see what can be done for OS X 10.7 through 10.9.

ZeroTier One.xcodeproj/project.pbxproj

@@ -272,6 +272,7 @@
 				COMBINE_HIDPI_IMAGES = YES;
 				INFOPLIST_FILE = "ZeroTier One/Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
+				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.zerotier.ZeroTier-One";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_OBJC_BRIDGING_HEADER = "ZeroTier One/ZeroTier One-Bridging-Header.h";
@@ -287,6 +288,7 @@
 				COMBINE_HIDPI_IMAGES = YES;
 				INFOPLIST_FILE = "ZeroTier One/Info.plist";
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/../Frameworks";
+				MACOSX_DEPLOYMENT_TARGET = 10.10;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.zerotier.ZeroTier-One";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_OBJC_BRIDGING_HEADER = "ZeroTier One/ZeroTier One-Bridging-Header.h";