fix carthage submodule support
fix carthage submodule support

DaveWoodCom/XCGLogger,pollarm/XCGLogger,adonoho/XCGLogger,cwoloszynski/XCGLogger,mottx/XCGLogger,mottx/XCGLogger,adonoho/XCGLogger,DaveWoodCom/XCGLogger,pollarm/XCGLogger,cwoloszynski/XCGLogger