Add missing filetype dependency

Author: bwohlberg

setup.py

@@ -45,7 +45,7 @@
 the Fast Iterative Shrinkage-Thresholding Algorithm (PGM).
 """
 
-install_requires = ['future', 'numpy', 'scipy', 'imageio', 'matplotlib']
+install_requires = ['future', 'numpy', 'scipy', 'imageio', 'filetype', 'matplotlib']
 on_rtd = os.environ.get('READTHEDOCS') == 'True'
 if on_rtd:
     print("Building on ReadTheDocs")