adds new functions and tests for load and supply matching
adds figures notebook file (committed without working to preserve initial state)
gets simulation module working with ipython notebooks
updates DateRange to date_range
updates tests
first steps at incorporating TMY3 radiation data
changed code in clear-sky angle calculations
almost added tests for azimuth angles
adds power_load.py and tmy3.py from the TMY3 repo to PyPVSim