Update Parsley.js to 1.1.16

Code from: https://github.com/guillaumepotier/Parsley.js

Includes the particularly useful addition of turning off errors with data-attribute 'data-show-errors'. https://github.com/guillaumepotier/Parsley.js/issues/214
Merge pull request #1302 from colourgarden/master

Update Parsley.js to 1.1.16