Implementing std.log

[so]

> For me, Logger needs to be simple but feature complete. Here is my ideal  
> syntax:
>
> Logger log = new Logger();
> log.warn("bewarned");
> log.error("error code: %d", 42);
> log.fatal("Derp");

Fine if you remove the first line, switching the output is something we  
rarely do, so we shouldn't mandate this for each use.

note("just a note :", 5);
note!warn("bewarned");
note!error(c, ", ", d);