Run the SwiftLint build phase with the --lenient flag

Running SwiftLint in "lenient" mode will only generate warnings, preventing the linter from causing the build to fail.
realm/SwiftLint#1322

SwiftGit2.xcodeproj/project.pbxproj

@@ -729,7 +729,7 @@
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 			shellPath = /bin/sh;
-			shellScript = "if which swiftlint >/dev/null; then\n    swiftlint\nelse\n    echo \"warning: SwiftLint is not installed\"\nfi";
+			shellScript = "if which swiftlint >/dev/null; then\n    swiftlint --lenient\nelse\n    echo \"warning: SwiftLint is not installed\"\nfi";
 		};
 /* End PBXShellScriptBuildPhase section */
 
@@ -1180,6 +1180,7 @@
 				C9CE0DD51E0710BD0053205D /* Release */,
 			);
 			defaultConfigurationIsVisible = 0;
+			defaultConfigurationName = Release;
 		};
 /* End XCConfigurationList section */
 	};