build: Updating npm dependencies for security issues

* Updated grunt to 1.0.4, addressing:
  * https://npmjs.com/advisories/788
  * https://npmjs.com/advisories/813
* Updated stylelint-config-wikimedia to 0.6.0, addressing:
  * https://npmjs.com/advisories/786

Committed package-lock.json (T179229) too.

Change-Id: Ia0419b7a1eac5aebba9313de6574aabd3cb36452

.gitignore

@@ -21,3 +21,4 @@ project.index
 ## Sublime
 sublime-*
 sftp-config.json
+.eslintcache

package.json

@@ -5,10 +5,10 @@
 	},
 	"devDependencies": {
 		"eslint-config-wikimedia": "0.12.0",
-		"grunt": "1.0.3",
+		"grunt": "1.0.4",
 		"grunt-banana-checker": "0.6.0",
 		"grunt-eslint": "21.0.0",
 		"grunt-stylelint": "0.10.1",
-		"stylelint-config-wikimedia": "0.5.0"
+		"stylelint-config-wikimedia": "0.6.0"
 	}
 }