Update Contributing.md to reflect OpenAPI conventions (issue #7)

[sdelatorrep]

Update Contributing.md to reflect OpenAPI conventions (issue #7).

[sdelatorrep]

Travis fails because it can't find the files (they are in my local repo but I can't create branches here).

[sdelatorrep]

Hi @mcupak , could you have a look at this, please? Thanks!

[mcupak]

@sdelatorrep Will do. Issue: #18

[mcupak]

@sdelatorrep I submitted #19 to fix the build issue. Please review and if OK rebase this PR onto it.

[sdelatorrep]

Hi @mcupak , I did the rebase but do you know why Travis is failing with this error?
The job exceeded the maximum log length, and has been terminated.
I saw you also got this error some days ago with the last PR you did but I don't know if you solved it somehow or just ignored it. Many thanks!

[sdelatorrep]

Hi @mcupak , please, see my comments here as some things have changed in the Swagger Validator repo.

[mcupak]

I'll wait for the review of ga4gh-beacon/specification#268, and we can then incorporate a similar solution here.

[mcupak]

@sdelatorrep #20

[sdelatorrep]

Hi @mcupak, could you merge this PR and do a release if there is nothing else missing? I don't have write access so I can't do any of these actions. Thanks!