Fix broken URL in SHOULDERS.md

[ruudk]

No description provided.

[markbates]

I'm merging this, because I want you to get contributor credit, but that file is actually auto generated by https://github.com/gobuffalo/buffalo/blob/master/grifts/shoulders.go, which is run when a new release is cut, so any changes to the SHOULDERS.md that are manually made will get wiped out. I would love a PR that fixed this automatically, if you're interested. :)

[ruudk]

I see the issue now, it's impossible to fix.

Only solution I see is this: When url is from github.com then split url and insert /tree/master/ between path 2 and 3 for the URL. Not sure what you think about it?

But then I think it would be better to just change the URL to always point to https://godoc.org/xxx instead.

[markbates]

I love the godoc idea! That’s brilliant. Let’s do that!

[ruudk]

Cool, created PR in #964