chore(doc): update reference grunt to gulp

.gitpod.yml

@@ -4,6 +4,6 @@ ports:
 tasks:
 - init: yarn install
   command: >
-    yarn grunt fastBuild &&
+    yarn gulp fastBuild &&
-    printf "\nWelcome to Learn Git Branching\nTo rebuild the app, simply run 'yarn grunt fastBuild' and reload index.html.\n\n" &&
+    printf "\nWelcome to Learn Git Branching\nTo rebuild the app, simply run 'yarn gulp fastBuild' and reload index.html.\n\n" &&
     python3 -m http.server 8000 2>/dev/null

README.md

@@ -70,9 +70,9 @@ Thus, if you build the app locally, all you have to do in order to run the app i
 ## Building yourself / Contributing Functionality
 
 For contributing core functionality in the app, you'll probably want to test your changes
-at least once before submitting a pull request. That means you'll need the "Grunt.js" build tool to build the app:
+at least once before submitting a pull request. That means you'll need the "gulp.js" build tool to build the app:
 
-https://gruntjs.com/getting-started
+https://gulpjs.com/docs/en/getting-started/quick-start
 
 You'll also need `yarn` to download all the dependencies of the project.
 
@@ -85,13 +85,13 @@ yarn install
 
 git checkout -b newAwesomeFeature
 vim ./src/js/git/index.js # some changes
-yarn grunt fastBuild # skips tests and linting, faster build
+yarn gulp fastBuild # skips tests and linting, faster build
 
 # after building you can open up your browser to the index.html
 # file generated and see your changes
 
 vim ./src/js/git/index.js # more changes
-yarn grunt build # runs tests and lint
+yarn gulp build # runs tests and lint
 
 git commit -am "My new sweet feature!"
 git push

package.json

@@ -6,7 +6,7 @@
   "author": "Peter Cottle <petermcottle@gmail.com>",
   "license": "MIT",
   "scripts": {
-    "test": "grunt test"
+    "test": "gulp test"
   },
   "repository": {
     "type": "git",