Test Valet commands (#1256)

* First attempt at testing CLI commands

* Apply fixes from StyleCI

* Protect from running locally

* Fix test

* wip

* wip

* wip

* wip

* wip

* Update app.php

* Create config folder and files for CLI tests

* Apply fixes from StyleCI

* Fix some formatting

* Fix imports

* Update all output() calls to use the writer passed in by the command

Ugly capture of all $outputs from commands, by passing them into `writer()` to be bound into the container, where they can then be pulled out from calls to `output()` and its buddies `info()`, `table()`, and `warning()`.

* Apply fixes from StyleCI

* Flesh out park command test

* Apply fixes from StyleCI

* Drop php 7.0 and 7.1

Co-authored-by: StyleCI Bot <bot@styleci.io>
Co-authored-by: Matt Stauffer <matt@tighten.co>

tests/ConfigurationTest.php

@@ -11,11 +11,14 @@
 
 class ConfigurationTest extends Yoast\PHPUnitPolyfills\TestCases\TestCase
 {
+    use UsesNullWriter;
+
     public function set_up()
     {
         $_SERVER['SUDO_USER'] = user();
 
         Container::setInstance(new Container);
+        $this->setNullWriter();
     }
 
     public function tear_down()