Two small patches

Hi,

Thanks a lot for this great package.

Here are two patches I would like to suggest:
- support for numpy arrays as cython args to allow time dependence using arrays. I use this in the following way: H.append([op/1e9, '(0 if (t<0 or t>100) else ch0[round(t)])']), where ch0 is a numpy array containing the actual waveform. It will be in the args dictionary given to mesolve/sesolve

Tensor:
- Add back support for the following: tensor([1, Qobj(...)]), which makes life easier when constructing operators programmatically (and used to work in earlier versions).

I'd be happy to hear what you think.

Regards,