Add templating support

[whitef0x0]

Should be able to compile and send emails rendered from templates.

[juanda99]

It's been a while... what's the current status?
I was trying to implement your code in my app, but I need localization for my app and it seems node-email-verification should need some changes.
Just saw https://github.com/crocodilejs/node-email-templates. Could something like this be implemented so we get templates & localization at the same time?
I could try to make a PR. Any recommendation?