Merge branch 'feature/drush-aliases-parent-directory' into '2.x'

Add parent directory creation when creating drush aliases' directory

<sites/all/> might not have been created yet (in drush8+d8 for instance)

See merge request !15

drush.py

@@ -75,7 +75,7 @@ def aliases():
     workspace = env.workspace
 
     if not h.fab_exists(role, drush_aliases):
-        h.fab_run(role, 'mkdir {}'.format(drush_aliases))
+        h.fab_run(role, 'mkdir -p {}'.format(drush_aliases))
     with h.fab_cd(role, drush_aliases):
         # Create aliases
         if h.fab_exists(role, '{}/aliases.drushrc.php'.format(drush_aliases)):