feat: Allow passing a callback for onDragOver as a prop (react-dropzone#326)

A callback for `onDragOver` event was missing in props. This PR adds it.

Closes react-dropzone#325

Author: husa

src/index.js

@@ -67,6 +67,10 @@ class Dropzone extends React.Component {
     } catch (err) {
       // continue regardless of error
     }
+
+    if (this.props.onDragOver) {
+      this.props.onDragOver.call(this, e);
+    }
     return false;
   }
 
@@ -310,6 +314,7 @@ Dropzone.propTypes = {
   onDropRejected: React.PropTypes.func,
   onDragStart: React.PropTypes.func,
   onDragEnter: React.PropTypes.func,
+  onDragOver: React.PropTypes.func,
   onDragLeave: React.PropTypes.func,
 
   children: React.PropTypes.node, // Contents of the dropzone

src/index.spec.js

@@ -165,19 +165,23 @@ describe('Dropzone', () => {
     it('should override onDrag* methods', () => {
       const dragStartSpy = spy();
       const dragEnterSpy = spy();
+      const dragOverSpy = spy();
       const dragLeaveSpy = spy();
       const component = mount(
         <Dropzone
           onDragStart={dragStartSpy}
           onDragEnter={dragEnterSpy}
+          onDragOver={dragOverSpy}
           onDragLeave={dragLeaveSpy}
         />
       );
       component.simulate('dragStart');
       component.simulate('dragEnter', { dataTransfer: { items: files } });
+      component.simulate('dragOver', { dataTransfer: { items: files } });
       component.simulate('dragLeave', { dataTransfer: { items: files } });
       expect(dragStartSpy.callCount).toEqual(1);
       expect(dragEnterSpy.callCount).toEqual(1);
+      expect(dragOverSpy.callCount).toEqual(1);
       expect(dragLeaveSpy.callCount).toEqual(1);
     });