Update README.md

Author: welir

README.md

@@ -16,6 +16,16 @@ Python logging library for realtime daily logging for python version 2.7
     log = Log('path to log dir', 'postfix log file name')
 
 # Usage
-    log.addToLog('Hello world')
+
+    # without log level param
+    Log.addToLog('Hello world')
+        2017-11-14 12:42:20,413 - INFO - Hello world
+    # warning log level
+    Log.addToLog('Hello world', 'warning')
+        2017-11-14 12:42:20,413 - WARNING - Hello world
+
+    # debug log level
+    Log.addToLog('Hello world', 'debug')
+        2017-11-14 12:42:20,413 - DEBUG - Hello world