Add moment.js third-party module via npm.

This is needed for timezone manipulations.  We may be able to replace
XDate with it in the future as well.

.eslintrc.json

@@ -14,6 +14,7 @@
         "Dropbox": false,
         "SockJS": false,
         "marked": false,
+        "moment": false,
         "i18n": false,
         "bridge": false,
         "page_params": false,

package.json

@@ -15,6 +15,8 @@
     "jquery": "2.2.3",
     "jquery-validation": "1.16.0",
     "katex": "0.7.1",
+    "moment": "2.18.1",
+    "moment-timezone": "0.5.12",
     "plotly.js": "1.19.2",
     "string.prototype.codepointat": "0.2.0",
     "underscore": "1.8.3",

version.py

@@ -1,2 +1,2 @@
 ZULIP_VERSION = "1.5.1+git"
-PROVISION_VERSION = '4.14'
+PROVISION_VERSION = '4.15'

zproject/settings.py

@@ -765,6 +765,8 @@ JS_SPECS = {
             'js/blueslip.js',
             'third/bootstrap/js/bootstrap.js',
             'js/common.js',
+            'node_modules/moment/moment.js',
+            'node_modules/moment-timezone/builds/moment-timezone-with-data.js',
         ],
         'output_filename': 'min/common.js'
     },