put package.json name back to webtorrent-app

webtorrent-www relies on this name. I originally changed it because I
thought the windows install builder was using it, but I pass all the
options into that explicitly now, and even pass an option to prevent it
from using package.json, so this should be okay.

package.json

@@ -1,5 +1,5 @@
 {
-  "name": "WebTorrent",
+  "name": "webtorrent-app",
   "description": "WebTorrent, the streaming torrent client. For OS X, Windows, and Linux.",
   "version": "0.1.0",
   "author": {