create list of contributors and populate from pull requestes

[mwcraig]

No description provided.

[Punyaslok]

@mwcraig Hi! Can you tell me how you're planning on executing this?
Do you plan on extracting all the names of contributors with merged pull requests for storage/display?

[souravsingh]

@mwcraig SymPy has a script which allows for adding Authors to the list based on the logs from git.It would be nice if we can make use of the script.

[mwcraig]

@souravsingh -- that sounds like a good plan, do you want to give it a try and open a PR? I think what we had in mind is a file like https://github.com/astropy/astropy/blob/master/docs/credits.rst

I don't think we need a copy of the script to do so in ccdproc itself, but if you could document how you generate it in the ccdproc wiki when you create the PR that would be great!

[souravsingh]

I have sent the PR. The PR is available at #313