Enable JSON logging

[bustikiller]

This pull request adds the option to log HTTP requests as JSON.

NOTE: http4 does not support ruby < 2.3.X, so the build for that combination has been flagged as "allow_failure"

[trusche]

Hi @bustikiller, I'd be happy to accept this with existing specs passing and new specs added to cover the added behaviour. Currently it breaks compact logging. See for example https://travis-ci.org/trusche/httplog/jobs/450821360.

[bustikiller]

Hi @trusche, this is still work in progress, I will fix the existing tests and write new tests for the added feature. Thanks!

[trusche]

Cool, just assign to me when you consider it done.

[bustikiller]

@trusche I think I have covered all the changes I wanted to do, along with the test cases. I cannot assign the PR to you because I don't have permissions.

I would love to hear some feedback from you.

[bustikiller]

@trusche did you have a chance to review this PR? I added a small change to identify application/pdf as binary, as it was causing some troubles with the transformation to JSON. It may be aligned with #61.

[trusche]

Hi @bustikiller, sorry I've been swamped. I'll try to get around to this this weekend.

[trusche]

There's a lot of repeated code across the various adapters now, all just calling various HttpLog methods in much the same order. It might be a good time to refactor that so that each adapter only needs to call a unified method and let the HttpLog module sort out how to log. The only thing that would have to be called separately from each adapter would be the connection logging.

I'm going to take a stab at that unless you want to.

[trusche]

Hi @bustikiller I've merged this into master and then added some refactorings on top. Would you let me know if master is working ok for you? I'm aiming to release this as 0.1.20 in a few days.