Add DiffStat functionality to remove certain fields from response

[codeaucafe]

With a recent change to the API, you can now remove certain response fields from the DiffStat API. For example you can include the query parameters: ?fields=-values.lines_added,-values.lines_removed to remove those fields the API returns.

It would be nice to have this functionality added to the DiffStat method.

@ktrysmt can you please assign this issue to me. I have already started working on this; I should have the PR ready in less than a week.

Thank you.

[ktrysmt]

Good information. I agreed it.

Thank you @DataDavD