Fixing bug related with trailing slash on UCF-101 dataset.

[Guillem96]

Now the dataset is not working properly because of this line of code indices = [i for i in range(len(video_list)) if video_list[i][len(self.root) + 1:] in selected_files].

Performing the len(self.root) + 1 only make sense if there is no trailing slash to self.root.

Here I attach an example of how this operation can remove an extra letter:

>>> root = 'data/ucf-101/videos'
>>> video_path = 'data/ucf-101/videos/activity/video.avi'
>>> video_path [len(root ) + 1:] # Works well
'activity/video.avi'
>>> root_with_trailing = 'data/ucf-101/videos/'
>>> video_path [len(root_with_trailing) + 1:] # We remove an extra letter
'ctivity/video.avi'

Appending the root path also to the selected files is a simple solution and make the dataset works with and without a trailing slash.

[fmassa]

Thanks!