Added set-e to run_all
Updated Mac Os dependencies setup details
Ignore error 'directory already exists' instead of ignoring any errors
dataset.py docstrings and comments
Removed unreachable 'return None'
Made is_image_file private and static (not really needed outside)
Merge pull request #1 from kolen/run_all_e

Added set-e to run_all
Merge pull request #3 from kolen/dataset-small-improvements

dataset.py small improvements
Merge pull request #2 from kolen/readme-macos-install-details

More details for MacOS dependencies setup instructions