Make native-promise-only a development dependency
Make native-promise-only a development dependency

It is only used by `test/stub-test.js`

mroderick/Sinon.JS,cjohansen/Sinon.JS,mroderick/Sinon.JS,fatso83/Sinon.JS,cjohansen/Sinon.JS,cjohansen/Sinon.JS,fatso83/Sinon.JS,mroderick/Sinon.JS,fatso83/Sinon.JS