more compatibility to older matlab versions

Author: bochinski

README.md

@@ -63,7 +63,7 @@ tracker.trackerName = 'iou-tracker';
 
 and run the script.
 
-Note that you still need a working python environment.
+Note that you still need a working python environment with numpy installed.
 You should obtain something like the following results for the 'DETRAC-Train' set:
 
 ##### DETRAC-Train Results

run_tracker.m

@@ -29,8 +29,8 @@
     ret = py.iou_tracker.track_iou_matlab_wrapper(py.numpy.array(baselinedetections(:).'), sigma_l, sigma_h, sigma_iou, t_min);
 
 catch exception
-    disp("error while calling the python tracking module: ")
-    disp(" ")
+    disp('error while calling the python tracking module: ')
+    disp(' ')
     disp(getReport(exception))
 end
 speed = ret{1};