added example that uses the new configurable log level feature.

examples/configure_log_level_example.rs

@@ -0,0 +1,13 @@
+#[macro_use]
+extern crate log;
+extern crate simple_logger;
+
+use log::LogLevel;
+
+fn main() {
+    simple_logger::init_with_level(LogLevel::Warn).unwrap();
+
+    warn!("This will be logged.");
+    info!("This will NOT be logged.");
+}
+