update circle and fix position key

[ABaldwinHunter]

Update circle.yml so that forked PRs can pass, following example in codeclimate-fixme.

Original goal was to be able to have CI build pass on this PR. The CI build - in a catch 22 of sorts - doesn't pass without the fix in that PR though, so I've added it here as well.

@codeclimate/review @jacobi007

[wfleming]

Should be noted that as-is this is a bit incomplete since the actual compiled bin has not been updated, and right now this project isn't configured to actually build itself on CI, just release. Same problem as I'm attempting to fix with codeclimate-community/codeclimate-govet#6. I think we should use a similar approach here, but in this case we can make the Dockerfile even simpler! I think this would work:

FROM scratch

ADD build/codeclimate-golint /usr/src/app/

RUN adduser -u 9000 -D app
USER app

CMD ["/usr/src/app/codeclimate-govet"]