Add try() and pass Github token to gh::gh() (related to #175)

[mrustl]

The changes done are related to #175.

As I frequently hit Github`s API limit for my use case I passed the Github token as additional argument to gh::gh() for issues/topics/readme and also added the missing try() as requested by @maelle for the issue/topic parts.

Finally I updated the package documentation with pkgdown.

[cboettig]

LGTM. @maelle I'll let you look over and merge this.

@maelle Unrelated but we could also consider relaxing our codecov targets so that they don't throw failed checks for small decreases in total test coverage like this... (I just learned how to do this over in RNeXML, check out the codecov.yml there)

[maelle]

@mrustl thanks! We haven't updated our contributing guidelines but the active branch is actually dev, could you PR to dev?

[maelle]

Also note that one can also save the token as an environment variable called GITHUB_PAT in which case gh will use it. :-)

[mrustl]

@maelle done! However, I don't know how I can see/fix what's causing the conflict in "guess_metadata.R"

[maelle]

Thanks but have you really changed 36 files? It's a bit hard to see the actual changes. Maybe it'd be easier to check out a new branch from dev and start again? Sorry!

[mrustl]

Sorry that I didn't get it that the changes I made were already in the dev branch. As you pointed out that 'GITHUB_TOKEN' can be used I not make any changes passing an additional 'auth_token' argument and close this pull request.

[maelle]

Ok! Sorry, will update the contributing guidelines, it was bad practice on my part.

You can still open a new PR to pass the argument if you wish. :-)

Thanks again, and thanks for reporting your use case!