Pre-deployment release for PyPI v0.0.3

This version will be tested in the field with a telescope this week. This will give us more data and experience to refine the current implementation and make improvements accordingly.

The changes done prior to its first application are

• Improve installation instructions and package description
• Improve logging in AutofocuserBase.save_focus_record
• Add more tests
• Add extremum_estimators.py, a module that provides classes
  for robustly estimating the minimum or maximum values in a set of
  noisy measurements using various techniques. These are used by the
  non NonParametricResponseAutofocuser class to find the minimum or
  maximum of the focus measurements.
• Add NonParametricResponseAutofocuser
• Correct a bug in interface/simulation.py
• Add smaller_is_better property to FocusMeasureOperator, indicating
  if smaller values correspond to better focus than larger for the given
  operator.