Define constant to reporttests.jl

[omus]

Avoids making users use joinpath(pkgdir(TestReports), "bin", "reporttests.jl") to determine the path to the runner script.

[oxinabox]

We should document this.

1. by mentioning it in the readme/docs
2. by putting a docstring on the constant

Once that is done, then LGTM

[omus]

I did a patch bump here as I think it was an oversight not to have a public facing reference to the reporttests.jl script if we intend for users of this package to use it.

[oxinabox]

I would describe this as a new feature.
Now it is much easier for a user to make use of this.
Version numbers are cheap

But I am not strongly committed to that

[omus]

Okay. As #113 is uncovering a couple of minor things to fix I'll drop the version bump here and add it later on.