Support Circle CI's wildcard contexts

[JasonEtco]

Looking through some logs I'm seeing a lot of statuses from Circle CI with a context following this scheme:

ci/circleci: SOMETHING USER DEFINED

Right now, ci-reporter will ignore all of those. It'd be great if the check for known contexts was a little looser:

https://github.com/JasonEtco/ci-reporter/blob/0911cefc1c26bcbd18870f94d12e23ff39cf343e/src/providers/Circle.js#L9-L11

https://github.com/JasonEtco/ci-reporter/blob/0911cefc1c26bcbd18870f94d12e23ff39cf343e/src/index.js#L25-L27