Enhancement: porter run --file URL

[nunix]

could porter run --file accept an URL as its input? (à la docker build)
This would allow, again like docker, to run with porter.yaml files stored on github (for example) and would allow testing, before building, without the need to download the said file or clone the repository.

Just an idea though, would totally understand if not applicable.

Thanks again for your work!

###EDIT
here is the workflow using a temporary file

[carolynvs]

Good idea! Thanks I'll add that to the backlog

[youreddy]

Hey @carolynvs, I took a stab at this issue in PR #187. Let me know if you have any feedback. Happy to make changes to it!

[nunix]

You are simply Amazing 💯