Add Symbol polyfill

Author: gf3

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Added contributors to *README*
 * Added CircleCI badge to *README*
 * Added yarn lockfile
+* Added polyfill for `Symbol`
 
 ### Changed
 

lib/moment-range.js

@@ -1,4 +1,5 @@
 import moment from 'moment';
+import Symbol from 'es6-symbol';
 
 //-----------------------------------------------------------------------------
 // Constants

package.json

@@ -64,6 +64,7 @@
     "karma-sourcemap-loader": "^0.3.7",
     "karma-webpack": "^1.8.0",
     "mocha": "^2.5.3",
+    "moment": "^2.17.1",
     "webpack": "^1.13.3"
   },
   "peerDependencies": {
@@ -78,5 +79,6 @@
     "url": "https://github.com/gf3/moment-range/raw/master/UNLICENSE"
   },
   "dependencies": {
+    "es6-symbol": "^3.1.0"
   }
 }

yarn.lock

@@ -1478,7 +1478,7 @@ es6-set@~0.1.3:
     es6-symbol "3"
     event-emitter "~0.3.4"
 
-es6-symbol@~3.1, es6-symbol@~3.1.0, es6-symbol@3:
+es6-symbol, es6-symbol@~3.1, es6-symbol@~3.1.0, es6-symbol@3:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/es6-symbol/-/es6-symbol-3.1.0.tgz#94481c655e7a7cad82eba832d97d5433496d7ffa"
   dependencies:
@@ -2630,6 +2630,10 @@ mocha@^2.5.3:
     supports-color "1.2.0"
     to-iso-string "0.0.2"
 
+moment:
+  version "2.17.1"
+  resolved "https://registry.yarnpkg.com/moment/-/moment-2.17.1.tgz#fed9506063f36b10f066c8b59a144d7faebe1d82"
+
 ms@0.7.1:
   version "0.7.1"
   resolved "https://registry.yarnpkg.com/ms/-/ms-0.7.1.tgz#9cd13c03adbff25b65effde7ce864ee952017098"