fix(semaphore): correct ENV variables

[jaredmoody]

and add additional options from available variables

Per semaphore docs, use the correct ENV variable names.

This partially addresses #55, in that the reporter should now read the correct environment variables on Semaphore, but does not address --service-job-id being ignored when --done is present.

The only thing I'm not sure about here is the service_build_url and service_job_url semantics mapping. On semaphore, the "job" is the individual process and the "workflow" is the entire build.

[coveralls]

Pull Request Test Coverage Report for Build 4660313599

• 6 of 6 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.05%) to 90.402%

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Totals
Change from base Build 4656075024:	0.05%
Covered Lines:	697
Relevant Lines:	771

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💛 - Coveralls

[jaredmoody]

Great, made those updates.