Put Deno call in separate module so it can be mocked

[teleclimber]

It's really hard to test out the the proper functioning of our test runner. It would be help if the part where we run Deno was taken out of the test runner and put in its own module. That way we could mock it nand have the mocked Deno behave in very specific ways. That way we can test to ensure our test runner picks up on all situations.

I'm referring to this stuff, currently found in run-test.js:

check() {
		return new Promise( (resolve, reject) => {
			exec('deno --allow-all '+this.test.script, {
				cwd: path.join(this.dir, this.test.cwd)
			}, (err, stdout, stderr) => {
				if(err) {
					console.error("bad test", this.test, err);
					reject(err);
				}
				resolve();
			});
		});
	}

	exec() {
		return new Promise( (resolve, reject) => {
			const t = this.test;
			exec('deno '+t.flags+' '+t.script, {
				cwd: path.join(this.dir, t.cwd)
			}, (err, stdout, stderr) => {
				if( err && this.errIsBadTest(err.message) ) reject(err.message);
				else if( err ) resolve(err.message);
				else resolve();
			});
		});
	}