config: change model_type and tokenizer_class

It uses BERT for model and RoBERTa for tokenizer now

config.json

@@ -11,10 +11,11 @@
   "intermediate_size": 768,
   "layer_norm_eps": 1e-05,
   "max_position_embeddings": 512,
-  "model_type": "bort",
+  "model_type": "bert",
   "num_attention_heads": 8,
   "num_hidden_layers": 4,
   "pad_token_id": 1,
+  "tokenizer_class": "Roberta",
   "type_vocab_size": 1,
   "vocab_size": 50265
 }