Add auto log uploader for CI workflow

[wohali]

Overview

This commit is intended to improve failure analysis in Travis and
Jenkins runs by uploading couch log files after failed test runs.

A new script has been added that, upon invocation from the top-level
directory, tars up all EUnit logfiles and the dev/logs/node1.log file.
It then constructs a document based on the running environment (Travis,
Jenkins, manual). The document is posted to a CouchDB instance running
on couchdb-vm.apache.org with credentials passed in the COUCHAUTH
environment variable.

The .travis.yml file has been updated to install the script's
prerequisites (python-requests) and with the secret credentials, and to
instruct travis to run the log uploader after any test failure. Similar
steps will be taken to reconfigure Jenkins after these changes are
merged to master.

The test/javascript/run harness had to be modified to terminate after
the first failure. This is because each new test wipes the logfile of
the previous run. All tests can still be run, regardless of failure, by
specifing the -a/--all flag, however it is expected that the reduction
in test suite execution time when a test fails will be appreciated by
many.

Testing recommendations

In the process of preparing this branch, Travis has already run multiple
times. I used a now-reverted checkin on the branch that forced a test
to fail to validate that the script worked correctly. One such build is:

https://travis-ci.org/apache/couchdb/builds/230990140

Interestingly, one of the jobs in that run actually encountered a new
test case failure:

https://travis-ci.org/apache/couchdb/jobs/230990141

Note that the URL of the uploaded tarball is displayed at the end
of the logfile (behind the after_failure twisty.)

For the duration of this PR, you can access the uploaded logs with
the username/password combination guest:guest. After merging,
CouchDB devs will be given access individually as desired and the
guest login will be disabled.

JIRA issue number

Take your pick of any JIRA ticket on which there is a currently failing test that we can't diagnose because the couch logfiles are missing.

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes;
• I will not forget to update rebar.config.script
  with the correct commit hash once this PR get merged.

[wohali]

URL of the interesting failure document: http:https://couchdb-vm.apache.org:5984/ci_errorlogs/travis-couchdb-230990141-2017-05-11T01%3A02%3A46.653747

Check out the couchlog.tar.gz attachment.

[wohali]

Ironically, another test failed in the PR itself (couch compress failure):

http:https://couchdb-vm.apache.org:5984/ci_errorlogs/travis-couchdb-230996527-2017-05-11T01%3A39%3A36.199020/couchlog.tar.gz

[janl]

Can we https this?

[janl]

This is very cool, +1

[davisp]

+1 to the PR and to the HTTPSification if possible.