Output TAP and LCOV files for CI reporting integration

[JamesMessinger]

I just discovered Zuul yesterday, and I'm really impressed with it. It has a lot of promise. Please keep up the great work!

When running Zuul in CI mode, it would be great if it could save its TAP and LCOV data as files, that way they can be read by CI reporting tools, such as Jenkins, Coveralls, Codacy, CodeClimate, etc. There are TAP reporters for all of the supported test frameworks (Mocha, QUnit, Jasmine, Tape), and Istanbul has built-in support for saving LCOV data to a file.

[defunctzombie]

Related issue: #217

Basically, I am open to someone improving this process (I haven't had the time to do so myself). There are a few approaches here. One of them could be to make the request to the coverage url endpoint to get the data files.

I am pretty sure saving would not be that tricky to implement overall.

[prabhg]

+1 for this issue. This is exactly what I am looking for. There should be a --coverage-dir kind of parameter to zuul to provide the export path of coverage reports.