Added in simpler email support by adding slm/mail from Jurian Sluiman

Enabled the SLM/Mail module and changed the version
The module's available at: https://github.com/juriansluiman/SlmMail
Added in logging support via monolog
Added support for an application cache

This is centred around using Redis as the backend cache, but provides a
rather flexible approach. The only thing which is specific is using
EnliteMonologService. Something doesn't seem quite right here. But for
the time being, I'm leaving it in.
Merge branch 'feature/add_redis_support' into develop