add abtest_get_data.py

add abtest_get_data.py

python/examples/imdb/abtest_get_data.py

+from paddle_serving_app.reader.imdb_reader import IMDBDataset
+imdb_dataset = IMDBDataset()
+imdb_dataset.load_resource('imdb.vocab')
+
+with open('test_data/part-0') as fin:
+    with open('processed.data', 'w') as fout:
+        for line in fin:
+            word_ids, label = imdb_dataset.get_words_and_label(line)
+            fout.write("{};{}\n".format(','.join([str(x) for x in word_ids]), label[0]))