There is a bug on paddle.v2.dataset.flowers

-  When training, just after a pass, training process does not go on.
-  There should not be "import paddle.v2 as paddle" in flowers.py file. There will cause import errors. 
-  There should be "import flowers"  in paddle/v2/dataset/__init__.py 
-  The test data should be train data, vice versa
