Use https instead of http for the url.

I figure it can't hurt.

Addresses https://app.asana.com/0/25429045350268/219824402827972

Auditors: kevinb

Test Plan:
None

Author: csilvers

package.json

@@ -4,7 +4,7 @@
   "description": "An accessibility visualization toolkit",
   "repository": {
     "type": "git",
-    "url": "http://github.com/Khan/tota11y.git"
+    "url": "https://github.com/Khan/tota11y.git"
   },
   "author": "Jordan Scales <[email protected]>",
   "devDependencies": {