Merge pull request #117 from amplitude/library-target-and-babel-rc

Add a umd library target and babel preset settings

Author: blazzy

.babelrc

@@ -0,0 +1,9 @@
+{
+  "presets": [
+    ["env", {
+      "targets": {
+        "browsers": ["ie >= 6"]
+      }
+    }]
+  ]
+}