A logger configured via an environment variable which writes to standard
error with nice colored output for log levels.
## Example
```
extern crate pretty_env_logger;
#[macro_use] extern crate log;
fn main() {
pretty_env_logger::init();
trace!("a trace example");
debug!("deboogging");
info!("such information");
warn!("o_O");
error!("boom");
}
```