cleanup and test systemdef
clean up and test ashraeiam
clean up and test physicaliam
remove getaoi from pvsystem. already in irradiance
clean up and test retrieve_sam
removing worthless old pvl tests that caused refactoring problems
clean up and test sapm_celltemp
add pvsystem tutorial
add io bytes parser for python3 compatibility
more python3 urllib parsing compatibility
clean up and test snlinverter. needs more work.
trying to clean up desoto and singlediode. too much of a mess. some pep8 changes
clean up and test sapm. needs more work.
clean up and test desoto and singlediode. needs more work
Merge branch 'feature/pvsystem-cleanup' into develop