Use numpy tolist() in DOS-family object as_dict() methods

[zooks97]

Use np.ndarray.tolist() method instead of python list() to convert density of state (Dos, FermiDos, CompleteDos) energies and densities in their as_dict() methods.

This fixes an issue where numpy numerical types (e.g. numpy.float64) exist in the results of {Dos, FermiDos, CompleteDos}.as_dict().

This allows these objects to be saved and stored more easily by mincePy Sci.

[coveralls]

Coverage decreased (-0.6%) to 83.036% when pulling ce0a5f1 on zooks97:dos-asdict-patch into df0f9ba on materialsproject:master.

[shyuep]

Thanks.