remove default js in "--watch-extensions" option; closes #3275
remove default js in "--watch-extensions" option; closes #3275

adamgruber/mocha,igwejk/mocha,boneskull/mocha,igwejk/mocha,adamgruber/mocha,mochajs/mocha,outsideris/mocha,mochajs/mocha,boneskull/mocha,outsideris/mocha,adamgruber/mocha,boneskull/mocha,mochajs/mocha