deps: Upgrade and move handlebars from static/third to npm

- Remove `handlebars.runtime.js` from static/third and fetch it from npm
- Upgrade `handlebars` to 3.0.3.

I change the test since there is a patch about line, written in
handlebars'
v2.0.0-beta.1 release note:
"Lines containing only block statements and whitespace are now removed."

Fixes zulip#1709.

frontend_tests/node_tests/templates.js

@@ -288,8 +288,7 @@ function render(template_name, args) {
     var all_html = '';
 
     html = render('bookend', args);
-
-    assert.equal($(html).text().trim(), "subscribed to stream\n    \n        \n            \n            Unsubscribe");
+    assert.equal($(html).text().trim(), "subscribed to stream\n    \n        \n            Unsubscribe");
 
     all_html += html;
 
@@ -300,7 +299,7 @@ function render(template_name, args) {
     };
 
     html = render('bookend', args);
-    assert.equal($(html).text().trim(), 'Not subscribed to stream\n    \n        \n            \n            Subscribe');
+    assert.equal($(html).text().trim(), 'Not subscribed to stream\n    \n        \n            Subscribe');
 
     all_html += '<hr />';
     all_html += html;

package.json

@@ -6,7 +6,7 @@
   "main": "",
   "dependencies": {
     "autosize": "3.0.20",
-    "handlebars": "1.3.0",
+    "handlebars": "3.0.3",
     "i18next": "3.0.0",
     "i18next-parser": "0.11.1",
     "i18next-xhr-backend": "0.5.4",