Improve javascript (src/parsley/ui.js).

1. Change png to svg.
2. Remove "sudo" on
```
sudo npm install -g docco
```
because
```
npm install -g grunt-cli
npm install -g bower
```
without "sudo" (single style).
3.`typeof fieldInstance.options.errorsContainer` can not be immediately and `'string'` and `'function'`.

If all changes correct run `grunt build-all`. Thanks!