Basis and integer types

[billbrod]

When trying to cross-validate on the basis's window_size (on branch development, making use of TransformerBasis), I called:

[nmo.basis.RaisedCosineBasisLog(8, mode='conv', window_size=ws) 
 for ws in np.arange(100, 301, 50)]

This fails, because we check isinstance(window_size, int) and the output of np.arange is not a default numpy integer. Should figure out the proper check here.