README.md in redis-mutex-2.0.0 vs README.md in redis-mutex-2.1.0

@@ -68,13 +68,14 @@
 
 There are a number of methods:
 
 ```ruby
 mutex = Redis::Mutex.new(key, options)    # Configure a mutex lock
-mutex.lock                                # Try to acquire the lock
-mutex.unlock                              # Try to release the lock
+mutex.lock                                # Try to acquire the lock, returns false when failed
 mutex.lock!                               # Try to acquire the lock, raises exception when failed
+mutex.unlock                              # Try to release the lock, returns false when failed
 mutex.unlock!                             # Try to release the lock, raises exception when failed
+mutex.locked?                             # Find out if resource already locked
 mutex.with_lock                           # Try to acquire the lock, execute the block, then return the value of the block.
                                           # Raises exception when failed to acquire the lock.
 
 Redis::Mutex.sweep                        # Remove all expired locks
 Redis::Mutex.with_lock(key, options)      # Shortcut to new + with_lock