Docstrings are text copied from the original MATLAB functions. Issues include:

1. inconsistent with the pvlib variable naming convention, e.g. GHI instead of ghi
2. not formatted to render properly in sphinx
3. inconsistent with actual function (columns names in returned data are not what is described in the table).

Additional issues to address:

1. parameter descriptions describe output with a hour-ending timestamp convention, but functions return data with hour-beginning timestamps
2. improve consistency in returned parameters among the read_tmy2, read_tmy3 and epw functions. Discussion here