Add S-needs-code-changes if travis build fails

[wafflespeanut]

This is a rebase of #88.

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Heads up! This PR modifies the following files:

• @jdm: handlers/status_update/init.py, travisciapiprovider.py, eventhandler.py, handlers/status_update/tests/build_status.json, newpr.py

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New code was committed to pull request.

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New code was committed to pull request.

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New code was committed to pull request.

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New code was committed to pull request.

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New code was committed to pull request.

[wafflespeanut]

@jdm I'm not sure whether you're gonna like this, because I couldn't find a way to have a module for TravisCiApiProvider without a circular dependency (and test it at the same time) without duplicating code (especially because it should be initialized at extract_globals_from_payload).

The easier solution was to integrate extract_globals_from_payload and the travis payload parsing into APIProvider itself, so that we can reuse the methods whenever we want.

[bors-servo]

☔ The latest upstream changes (presumably #125) made this pull request unmergeable. Please resolve the merge conflicts.