… the electric field (wavefront) and intensity

- the PhysicalFresnelWavefront class also implements some additional features like beam quality parameter determination
- made necessary changes to include the class in the core package
- added an IPython notebook to demonstrate the what the class can do

- incorporated the suggested changes

Newest changes from head fork

* master:
  Big update: PEP8 compatible Instrument API
  Substantial update to Semi-Analytic Coronagraph code; fixes #169
  misc improvements to DM classes
  fix py2.7 compat for ContinuousDM; add test for HexDM
  Initial commit of hexagonally segmented DM
  Initial commit of continuous deformable mirror class
  minor fix to prev commit [ci skip]
  add ArrayOpticalElement class [ci skip]
  fix #231 about markcentroid overriding imagecrop in display_psf [ci skip]
  fix #231 about markcentroid overriding imagecrop in display_psf
  increment minimal numpy ver to 1.10; see #244
  minor code and whitespace cleanup [ci skip]
  Quick fix on utils.py measure_radius_at_ee function - using poppy's radial_profile function instead of webbpsf's and including new function in __all__ list
  Added tutorial and unit test for the new measure_radius_at_ee function
  Added inverse of measure_ee function in poppy/utils.py named measure_radius_at_ee

# Conflicts:
#	poppy/__init__.py

- fixed a bug in the M2 calculation