Accept all `T: fmt::Display` in `message` argument, not just `&str`.

[Kixunil]

Advantages of this interface:

• No need to create separate string for simple things
• More efficient code - fewer allocations

Something that could be considered disadvantage is the ability to directly log surprising things, like u32 etc. My personal opinion is that it's not much of a problem.

Note that this is perfectly backward-compatible because &str: fmt::Display.

[Geal]

good idea, thanks

[Kixunil]

YAW! Do you have an ETA of release?