pvlib-python: 0.2.0

This is a major release from 0.1 and includes a large number of API changes, several new features and enhancements along with a number of bug fixes. We recommend that all users upgrade to this version.

Due to the large number of API changes, you will probably need to update your code.

• Change variable names to conform with new Variables and style rules wiki <https://github.com/pvlib/pvlib-python/wiki/Variables-and-style-rules>_. This impacts many function declarations and return values. Your existing code probably will not work! (:issue:37, :issue:54).
• Move dirint and disc algorithms from clearsky.py to irradiance.py (:issue:42)
• Mark some pvsystem.py methods as private (:issue:20)
• Make output of pvsystem.sapm_celltemp a DataFrame (:issue:54)

• Add conda installer
• PEP8 fixups to solarposition.py and spa.py (:issue:50)
• Add optional projection_ratio keyword argument to the haydavies calculator. Speeds calculations when irradiance changes but solar position remains the same (:issue:58)
• Improved installation instructions in README.

• fix local build of the documentation (:issue:49, :issue:56)
• The release date of 0.1 was fixed in the documentation (see :ref:whatsnew_0100)
• fix casting of DateTimeIndex to int64 epoch timestamp on machines with 32 bit python int (:issue:63)
• fixed some docstrings with failing doctests (:issue:62)

• Will Holmgren
• Rob Andrews
• bmu
• Tony Lorenzo