Update Installing.md (#3870)
Update Installing.md (#3870)

Some extra help concerning a common issue that occurs with fresh install of Xcode + react native 0.56. https://github.com/react-community/create-react-native-app/issues/316#issuecomment-351371080
Jpoliachik/react-native-navigation,wix/react-native-navigation,chicojasl/react-native-navigation,chicojasl/react-native-navigation,chicojasl/react-native-navigation,wix/react-native-navigation,guyca/react-native-navigation,chicojasl/react-native-navigation,wix/react-native-navigation,guyca/react-native-navigation,3sidedcube/react-native-navigation,chicojasl/react-native-navigation,wix/react-native-navigation,thanhzusu/react-native-navigation,Jpoliachik/react-native-navigation,3sidedcube/react-native-navigation,thanhzusu/react-native-navigation,Jpoliachik/react-native-navigation,guyca/react-native-navigation,ceyhuno/react-native-navigation,3sidedcube/react-native-navigation,Jpoliachik/react-native-navigation,thanhzusu/react-native-navigation,Jpoliachik/react-native-navigation,wix/react-native-navigation,ceyhuno/react-native-navigation,thanhzusu/react-native-navigation,wix/react-native-navigation,thanhzusu/react-native-navigation,ceyhuno/react-native-navigation,ceyhuno/react-native-navigation,ceyhuno/react-native-navigation,chicojasl/react-native-navigation,thanhzusu/react-native-navigation,Jpoliachik/react-native-navigation,guyca/react-native-navigation,ceyhuno/react-native-navigation,3sidedcube/react-native-navigation