Logging

Added in the dependencies for logging and proved that logging
functionality is working. Should be able to close issue #23.

src/main.rs

@@ -1,5 +1,9 @@
+extern crate log;
 extern crate sdl2;
 
+use env_logger::Builder;
+use log::{error, info, warn, LevelFilter};
+
 use sdl2::event::Event;
 use sdl2::keyboard::Keycode;
 use sdl2::pixels::Color;
@@ -105,6 +109,12 @@ Flags:
         level.linedefs[test_linedef].always_automap()
     );
 
+    Builder::new().filter_level(LevelFilter::Info).init();
+
+    info!("Test of INFO log!");
+    warn!("Test of WARN log!");
+    error!("Test of ERROR log!");
+
     let sdl_context = sdl2::init().unwrap();
     let video_subsystem = sdl_context.video().unwrap();