Improve Futures class code coverage

[Ivruix]

Added test for asString method.

[Ivruix]

While doing so I've noticed some inconsistencies with the ordering of the group and artifact variables. In the Futures class itself there is this line:

Logger.info(
    this, "Started processing of %s:%s...",
    group, artifact
);

And later, with the artifact and group swapped:

Logger.info(
    this, "Finished processing of %s:%s",
    artifact, group
);

Also in the FuturesTest.java file in testSimpleScenario method the order of artifact and group is incorrect, as the Future class expects the first argument to be group:

new Futures(
    (artifact, group) -> input -> new RsPage(
        new RqFake(),
        "wait",
        () -> new IterableOf<>(
            new XeAppend("group", group),
            new XeAppend("artifact", artifact)
        )
    )
).apply("a", "g").get().apply("test"),

It doesn't matter for the purposes of the test, but it might confuse someone, as it did for me. I can make a small PR fixing these issues if you'd like.

[Ivruix]

@yegor256 please take a look. I'm not sure why ubuntu builds failed, but others have passed. They timed out on AsyncReportsTest test which I did not modify.

[yegor256]

@Ivruix thanks for this one! Indeed, will be great if you fix the ordering in a new PR