choose template straight from cli

Hi, again.

I do not really like how `-c` option behaves, right now it only allows to interactively choose template, but what would be more useful, as I think, is to allow to set desired template straight from cli, for instance:

`facio -n test -c mycooltemplate`

facio.cfg:
```
[template]
mycooltemplate=/path/to/my/really/cool/template
```

I'd written some code about 2 months ago just for myself, but after merging with your master branch my changes are not working due to massive code base change.
So I thought this time I should file an issue.

What I think is the best way in this situation is to check if `-c` argument is in defined template otherwise force user to choose from interactive prompt.

Tell me what do you think?