run the yarn-installed grunt version instead of relying on local grunt

(attempt to fix stuff #1 (closed))

cc @laurent.heirendt

.ci/deploy.sh

@@ -55,10 +55,10 @@ do
                 ln -s ../../theme theme
 
                 # install npm
-                yarn global add grunt-cli generator-reveal
+                yarn global add grunt-cli generator-reveal grunt
                 yarn install
 
-                grunt dist
+                yarn exec grunt dist
                 cp -rL public/* $rootDir/public/$BLADE/$version/.
 
                 echo " > latest built for file set ${BLADE}"