Fix default border color.

Author: overtrue

stubs/defaultConfig.stub.js

@@ -238,7 +238,7 @@ module.exports = {
       '8': '8px',
     },
     borderColor: theme => {
-      return global.Object.assign({ default: theme('colors.gray.700', 'currentColor') }, theme('colors'))
+      return global.Object.assign({ default: theme('colors.gray.300', 'currentColor') }, theme('colors'))
     },
     borderRadius: {
       none: '0',