shorten mnist simple

Author: zsdonghao

example/tutorial_mnist_simple.py

@@ -37,8 +37,8 @@
 
 # define the optimizer
 train_params = network.all_params
-train_op = tf.train.AdamOptimizer(learning_rate=0.0001, beta1=0.9, beta2=0.999,
-                            epsilon=1e-08, use_locking=False).minimize(cost, var_list=train_params)
+train_op = tf.train.AdamOptimizer(learning_rate=0.0001
+                    ).minimize(cost, var_list=train_params)
 
 # initialize all variables in the session
 tl.layers.initialize_global_variables(sess)