Closes #6. Fix dragging issues where cells are variables heights.

Previously the delegate had to keep track of the height of the cell
being dragged. Adding the draggingRowHeight property allows easier
manipulation in cases where cells are variable heights.

BVReorderTableView.h

@@ -44,6 +44,7 @@
 @interface BVReorderTableView : UITableView
 
 @property (nonatomic, assign) id <ReorderTableViewDelegate> delegate;
+@property (nonatomic, assign) CGFloat draggingRowHeight;
 @property (nonatomic, assign) BOOL canReorder;
 
 @end

BVReorderTableView.m

@@ -30,6 +30,7 @@ @interface BVReorderTableView ()
 @property (nonatomic, strong) NSTimer *scrollingTimer;
 @property (nonatomic, assign) CGFloat scrollRate;
 @property (nonatomic, strong) NSIndexPath *currentLocationIndexPath;
+@property (nonatomic, strong) NSIndexPath *initialIndexPath;
 @property (nonatomic, strong) UIImageView *draggingView;
 @property (nonatomic, retain) id savedObject;
 
@@ -46,7 +47,14 @@ - (void)cancelGesture;
 @implementation BVReorderTableView
 
 @dynamic delegate, canReorder;
-@synthesize longPress, scrollingTimer, scrollRate, currentLocationIndexPath, draggingView, savedObject;
+@synthesize longPress;
+@synthesize scrollingTimer;
+@synthesize scrollRate;
+@synthesize currentLocationIndexPath;
+@synthesize draggingView;
+@synthesize savedObject;
+@synthesize draggingRowHeight;
+@synthesize initialIndexPath;
 
 - (id)init {
     return [self initWithFrame:CGRectZero];
@@ -109,6 +117,7 @@ - (void)longPress:(UILongPressGestureRecognizer *)gesture {
     if (gesture.state == UIGestureRecognizerStateBegan) {
 
         UITableViewCell *cell = [self cellForRowAtIndexPath:indexPath];
+        self.draggingRowHeight = cell.frame.size.height;
         [cell setSelected:NO animated:NO];
         [cell setHighlighted:NO animated:NO];
 
@@ -146,6 +155,7 @@ - (void)longPress:(UILongPressGestureRecognizer *)gesture {
         [self insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationNone];
         self.savedObject = [self.delegate saveObjectAndInsertBlankRowAtIndexPath:indexPath];
         self.currentLocationIndexPath = indexPath;
+        self.initialIndexPath = indexPath;
         [self endUpdates];
 
         // enable scrolling for cell
@@ -231,7 +241,14 @@ - (void)updateCurrentLocation:(UILongPressGestureRecognizer *)gesture {
     location  = [gesture locationInView:self];
     indexPath = [self indexPathForRowAtPoint:location];
 
-    if (indexPath && ![indexPath isEqual:self.currentLocationIndexPath]) {
+    if ([self.delegate respondsToSelector:@selector(tableView:targetIndexPathForMoveFromRowAtIndexPath:toProposedIndexPath:)]) {
+        indexPath = [self.delegate tableView:self targetIndexPathForMoveFromRowAtIndexPath:self.initialIndexPath toProposedIndexPath:indexPath];
+    }
+
+    NSInteger oldHeight = [self rectForRowAtIndexPath:self.currentLocationIndexPath].size.height;
+    NSInteger newHeight = [self rectForRowAtIndexPath:indexPath].size.height;
+
+    if (indexPath && ![indexPath isEqual:self.currentLocationIndexPath] && [gesture locationInView:[self cellForRowAtIndexPath:indexPath]].y > newHeight - oldHeight) {
         [self beginUpdates];
         [self deleteRowsAtIndexPaths:[NSArray arrayWithObject:self.currentLocationIndexPath] withRowAnimation:UITableViewRowAnimationAutomatic];
         [self insertRowsAtIndexPaths:[NSArray arrayWithObject:indexPath] withRowAnimation:UITableViewRowAnimationAutomatic];