fix grunt local

contribute.py

@@ -76,12 +76,11 @@ def main(date, name):
     else:
         click.echo(' > Gruntfile already exists.')
 
-
+    os.chdir(fullPath)
     # launch the presentation deck
     if not os.path.exists(os.path.join(fullPath, 'node_modules')):
         click.echo(' > Installing dependencies ... ')
-        os.system('yarn add -g grunt-cli generator-reveal')
-        os.system('yarn')
+        os.system('yarn add grunt generator-reveal')
         click.echo(' > All dependencies installed.')
     else:
         click.echo(' > All dependencies already installed.')