add unit/integrted tests for dpc

Yes, an optional parameter might be better.

> On Dec 1, 2014, at 3:46 PM, Thomas A Caswell <notifications@github.com> wrote:
> 
> In skxray/dpc.py:
> 
> > +
> > +    dy : float
> > +        Scanning step size in y direction (in micro-meter).
> > +
> > +    energy : float
> > +        Energy of the scanning x-ray in keV.
> > +
> > +    roi : numpy.ndarray, optional
> > +        Upper left co-ordinates of roi's and the, length and width of roi's
> > +        from those co-ordinates.
> > +
> > +    bad_pixels : list
> > +        Store the coordinates of bad pixels.
> > +        [(1, 5), (2, 6)] --> 2 bad pixels --> (1, 5) and (2, 6)
> > +
> > +    solver : string
> Do you really want to make this a mandatory argument?
> 
> —
> Reply to this email directly or view it on GitHub <https://github.com/Nikea/scikit-xray/pull/177/files#r21117983>.
> 

--
Best Regards,

  Cheng Chang 
  Computer Engineering, Stony Brook University
  Computer Science Group, Computational Science Center, Brookhaven National Laboratory
  Tel：(001) 631-885-4922