Make cache directory if it doesn't already exist

[retlehs]

example with wp_mkdir_p

[retlehs]

this is still an issue, at least with when trying to use sage 10 for the first time. you need to create the cache directory otherwise you get file_put_contents errors

[QWp6t]

https://github.com/roots/acorn/blob/master/config/app.php#L18

Set it to true.

It shouldn't be an issue in Sage now since latest Sage should have it enabled in non-production: https://github.com/roots/sage/blob/10.0.0-dev/config/app.php#L44