Update README.md for gradle builds
Update README.md for gradle builds

Update README in order to describe new sys requirements.

tsvetie/nativescript-cli,tsvetie/nativescript-cli,NathanaelA/nativescript-cli,tsvetie/nativescript-cli,tsvetie/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli,tsvetie/nativescript-cli,NathanaelA/nativescript-cli,NathanaelA/nativescript-cli,NativeScript/nativescript-cli