add textCNN model to __init__.py (tensorflow#1421)

Author: yuwen-yan

tensor2tensor/models/__init__.py

@@ -38,6 +38,7 @@
 from tensor2tensor.models import revnet
 from tensor2tensor.models import shake_shake
 from tensor2tensor.models import slicenet
+from tensor2tensor.models import text_cnn
 from tensor2tensor.models import transformer
 from tensor2tensor.models import vanilla_gan
 from tensor2tensor.models import xception