Add link to pre-minified FastClick - hopefully addressing #192

@2ix, @mlms13 - I know you ideally wanted a pre-minified version of the code committed into the repository but within FT Labs we feel that this isn't something we want to do - and the other open source repositories we have that have committed built/minified bundles will have those files phased out...

I've added a link to [a minified version of FastClick](http://build.origami.ft.com/bundles/js?modules=fastclick) on the readme, which will be automatically updated whenever we publish a new version.  I hope this will be acceptable compromise.