Improve console output when generating mixins

[tpluscode]

Currently when generating mixins the console reads

`Module` generated in 149ms
`MyElement` generated in 78ms

It would be nice to actually put the mixin's name in the output and not simply Module fear each mixin.

[Buslowicz]

What about multiple mixins per file? Should we maybe instead of Module place a source file name or path?

[tpluscode]

I'd expect multiple logs. One for each generated mixin.

[Buslowicz]

This could be confused to multiple files output. What do you think about something more like this?

MyMixin1, MyMixin2, MyMixin3 saved to `mixins-file.html` (generated in 149ms)

[tpluscode]

Sure, that would work too. I don't have a strong opinion

[Buslowicz]

Okie dokie, I'll queue that up :).