Add a little information about the project, some brief (probably
incomplete) setup instructions, installation, and license information.

Add COPYING file and license notices to sources.

Make it clear that we want to run on local localhost (and not
"0.0.0.0").

Initialise a new 'stderrlog' and log all errors to the log.

For logging capabilities. 'stderrlog' seemed like a reasonable option to
go with, even though it only logs to STDERR, given that I only feel the
need to log to STDERR.

I had used `to_owned()` previously in other projects, but after looking
up the difference (again probably), I decided that it seems better to
use `to_owned()`.

References:

https://users.rust-lang.org/t/to-string-vs-to-owned-for-string-literals/1441/6
http://www.lowlevelmanager.com/2016/02/rust-tostring-vs-toowned-for-string.html

Realised that the reason why I was getting a dead code warning from
`Job::new` was not just because I wasn't using it, but because I was
meant to use it somewhere. Remove the duplicate work going on in
`request_job()` and replace it with a call to `Job::new()` instead.

Now that `update_commit_status()` takes the GitHub API token as an
argument, pass in a fake one in our test.

Now that the Jenkins API URL is getting passed in via command line and
function argument, update the tests to pass it in directly.

Remove the test/non-test versions of `jenkins_url` from
`find_and_track_build_and_update_status()` because we can pass in the
mock URL directly to the `get_jobs()` and `request_job()` functions in
tests.

Make the `jenkins_url` argument to
`find_and_track_build_and_update_status()` not a reference so that we
don't have to reset it in the function to a `to_owned()` version.