Fix issue #12 - function custom props.

Author: jsillitoe

.babelrc

@@ -1 +1 @@
-{ "presets": ["es2015", "react"] }
+{ "presets": ["es2015", "react", "stage-3"] }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-currency-input",
-  "version": "1.2.3",
+  "version": "1.2.4",
   "description": "React component for inputing currency amounts",
   "main": "lib/index.js",
   "scripts": {
@@ -38,6 +38,7 @@
     "babel-cli": "^6.18.0",
     "babel-preset-es2015": "^6.9.0",
     "babel-preset-react": "^6.5.0",
+    "babel-preset-stage-3": "6.22.0",
     "babel-register": "^6.9.0",
     "babelify": "^7.3.0",
     "browserify": "^13.0.1",

src/index.js

@@ -49,7 +49,7 @@ const CurrencyInput = React.createClass({
      * @returns {{ maskedValue: {String}, value: {Number}, customProps: {Object} }}
      */
     prepareProps(props) {
-        let customProps = JSON.parse(JSON.stringify(props)); //not as clean, but better support
+        let customProps = {...props}; // babeljs converts to Object.assign, then polyfills.
         delete customProps.onChange;
         delete customProps.value;
         delete customProps.decimalSeparator;