on-drag-start and on-drag-end callbacks don't work with minified version

[n3ko1]

When using the minified version of this library, passed functions via on-drag-start or on-drag-end are not found by $parse and thus not executed.

Also, the documentation for this feature is incorrect:
https://github.com/jellekralt/angular-drag-scroll#events

If one uses onDragStart (camel case), this equates to $attributes.ondragstart (lower case) in the directives link function. This will be undefined! Correct usage is: on-drag-start="doStuff()".