Update acf_repeater_collapser_admin.js

Added Support for Flexible Content fields.
Update acf_repeater_collapser_admin.css

Fixed janky styles with button placement. ( i.e. https://dl.dropbox.com/s/2x3ckmfbjp3q6qp/2013-04-11_at_1.58.16_PM.png )
Merge pull request #4 from ofdesks/master

Support for Flexible Content fields and CSS tweak for button placement