javascript: transpile compatible JS for all browsers we support

.babelrc

@@ -3,7 +3,16 @@
     ["env", {
       "modules": false,
       "targets": {
-        "browsers": "> 1%",
+        // See config/browser.rb
+        "browsers": [
+          "> 1%",
+          "Chrome 40",
+          "IE 11",
+          "Edge 12",
+          "Firefox 45",
+          "Safari 8",
+          "iOS 8"
+        ],
         "uglify": true
       },
       "useBuiltIns": true

config/initializers/browser.rb

@@ -1,3 +1,4 @@
+# See .babelrc
 Browser.modern_rules.clear
 Browser.modern_rules << -> b { b.chrome? && b.version.to_i >= 40 }
 Browser.modern_rules << -> b { b.ie?([">=11"]) }