modify plugins_url() call to use paramters

Modify plugins_url() call to use parameters rather than
appending the rest of the path. This would allow a developer
to filter the call to plugins_url(), specifically to address the issue in
http://wordpress.org/support/topic/stylesheet-error-1?replies=5
By passing in these parameters, one could identify the correct
call to plugins_url() and filter it as necessary (in this case replacing
https:// with http://)