Add better lint checking.

Summary:
Make the lint checker check more files. Also, make arc run the
linter.

Test Plan:
 - `arc lint`
 - `make lint`

Reviewers: kevinb, alpert

Reviewed By: alpert

Differential Revision: https://phabricator.khanacademy.org/D17509

contrib/auto-render/auto-render-spec.js

@@ -1,3 +1,9 @@
+/* global beforeEach: false */
+/* global jasmine: false */
+/* global expect: false */
+/* global it: false */
+/* global describe: false */
+
 var splitAtDelimiters = require("./splitAtDelimiters");
 
 beforeEach(function() {
@@ -28,6 +34,7 @@ beforeEach(function() {
                         var correct = result[i];
 
                         var good = true;
+                        var diff;
 
                         if (real.type !== correct.type) {
                             good = false;

contrib/auto-render/auto-render.js

@@ -1,3 +1,5 @@
+/* global katex */
+
 var splitAtDelimiters = require("./splitAtDelimiters");
 
 var splitWithDelimiters = function(text, delimiters) {
@@ -48,9 +50,8 @@ var renderElem = function(elem, delimiters, ignoredTags) {
             if (shouldRender) {
                 renderElem(childNode, delimiters, ignoredTags);
             }
-        } else {
-            // Something else, ignore
         }
+        // Otherwise, it's something else, and ignore it.
     }
 };