Limit on convergence, corrected min mask.

 - If convergence could not be reached, until now FitsStats would
   continue sigma-clipping! But now, there is an internal limit that
   can be set in `fitsstats.h`. It is currently set to 30.

 - Added a Sum output in the simple statistics report. This can be
   useful sometimes.

 - Corrected a few problems in applymask(). I had mistakenly forgot to
   check what is in the pointer `m`, not the pointer its self! I also
   added a report saying how many masked pixels were not considered.

 - The outputs would be printed no matter if the user had asked for a
   it or not. Now the outputs are only printed if `-q` or `--quiet`
   are not called.

 - Correted the quantile treatment in finding the bins. It would
   mistakenly use only the histogram quantile value for the minimum
   and maximum bin.