Update instructions from using go get to using go install

[hansgylling]

Describe the bug The project have some old files with instructions that tells the reader to use go get -u to install revive. I believe this should say go install nowadays. The files I have seen so far are DEVELOPING.md and .github/ISSUE_TEMPLATE/bug_report.md, but it could be a good idea to look for more instances with grep -r -F 'go get'

[mgechev]

Hey @hansgylling do you want to open a PR with the update?

[hansgylling]

Yes, I was thinking I could fix it myself. I didn't have much time when writing the bug, but could do it now. I have ran the grep command I suggested and didn't find any other file.

I will say that I'm not used to Github (we use Gitlab at work) and I haven't made any pull request on Github yet, so I will need to figure that out and may make some mistakes along the way. We'll see.

[chavacava]

Hi @hansgylling, I'll be glad to help you with the PR process.

[doniacld]

@chavacava I think the issue is fixed, you can close it.

[chavacava]

@doniacld there are still some references to go get in the project documentation

[attiss]

@chavacava I'd be happy contribute these updates to the docs.

[attiss]

https://github.com/mgechev/revive/pull/750

[hansgylling]

Thanks for doing this. I said I would do it, but I've been very busy with work and life.