Adds multisite test environment to CI

Adds Robo command to run multisite tests locally and on CI

.circleci/apache/mailpoet.loc.conf

@@ -1,6 +1,4 @@
-Listen 8080
-
-<VirtualHost *:8080>
+<VirtualHost *:80>
   UseCanonicalName Off
   ServerName mailpoet.loc
   DocumentRoot /home/circleci/mailpoet/wordpress
@@ -8,6 +6,9 @@ Listen 8080
   LogLevel notice
 
   <Directory /home/circleci/mailpoet/wordpress>
+    Options Indexes FollowSymLinks
+    AllowOverride All
+    RewriteEngine On
     Require all granted
   </Directory>
 </VirtualHost>