Adds translation pipeline (#3419)

* fix merge conflicts

* add t5 summarization example

* change parameters for t5 summarization

* make style

* add first code snippet for translation

* only add prefixes

* add prefix patterns

* make style

* renaming

* fix conflicts

* remove unused patterns

* solve conflicts

* fix merge conflicts

* remove translation example

* remove summarization example

* make sure tensors are in numpy for float comparsion

* re-add t5 config

* fix t5 import config typo

* make style

* remove unused numpy statements

* update doctstring

* import translation pipeline

src/transformers/__init__.py

@@ -116,6 +116,7 @@ from .pipelines import (
     SummarizationPipeline,
     TextClassificationPipeline,
     TokenClassificationPipeline,
+    TranslationPipeline,
     pipeline,
 )
 from .tokenization_albert import AlbertTokenizer