Added functionality to allow inputting a mag image, mag index, igram image, and igram index, and skipping the processing, in addition to being able to input a mag and int filename

Hi Sreejith, 

You can reject this pull request if you want. Basically I changed your find_delta code so that I can do the processing of the igram and magnetogram before hand, and then read the image arrays and index structures into your code. That gives me more flexibility with the processing I can do.

I forked your repository and I am using my fork to run your code in real time on my machine.

Cheers,
-Paul