title: Unable to install coremltools
body: <p>I am trying to convert a pb file to a coreml file. to do this i need to install coremltools. However, when i try to install it by pip it comes up with this error :
       ERROR: Could not find a version that satisfies the requirement coremltools (from versions: none)
  ERROR: No matching distribution found for coremltools</p>
  
  <p>i have tried to install it in a python 2.7 environment, still no joy</p>
  
  <p>pip install coremltools
  Collecting coremltools
    ERROR: Could not find a version that satisfies the requirement coremltools (from versions: none)
  ERROR: No matching distribution found for coremltools
  Rorys-MBP:~ roryhodgson$</p>