Replace meta_tags.csv with hparams.yaml (#1271)

* Add support for hierarchical dict

* Support nested Namespace

* Add docstring

* Migrate hparam flattening to each logger

* Modify URLs in CHANGELOG

* typo

* Simplify the conditional branch about Namespace

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* Update CHANGELOG.md

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* added examples section to docstring

* renamed _dict -> input_dict

* mata_tags.csv -> hparams.yaml

* code style fixes

* add pyyaml

* remove unused import

* create the member NAME_HPARAMS_FILE

* improve tests

* Update tensorboard.py

* pass the local test w/o relavents of Horovod

* formatting

* update dependencies

* fix dependencies

* Apply suggestions from code review

* add savings

* warn

* docstrings

* tests

* Apply suggestions from code review

* saving

* Apply suggestions from code review

* use default

* remove logging

* typo fixes

* update docs

* update CHANGELOG

* clean imports

* add blank lines

* Update pytorch_lightning/core/lightning.py

Co-authored-by: Adrian Wälchli <aedu.waelchli@gmail.com>

* Update pytorch_lightning/core/lightning.py

Co-authored-by: Adrian Wälchli <aedu.waelchli@gmail.com>

* back to namespace

* add docs

* test fix

* update dependencies

* add space

Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>
Co-authored-by: Adrian Wälchli <aedu.waelchli@gmail.com>

docs/source/test_set.rst

@@ -21,10 +21,9 @@ To run the test set on a pre-trained model, use this method.
 
 .. code-block:: python
 
-    model = MyLightningModule.load_from_metrics(
-        weights_path='/path/to/pytorch_checkpoint.ckpt',
-        tags_csv='/path/to/test_tube/experiment/version/meta_tags.csv',
-        on_gpu=True,
+    model = MyLightningModule.load_from_checkpoint(
+        checkpoint_path='/path/to/pytorch_checkpoint.ckpt',
+        hparams_file='/path/to/test_tube/experiment/version/hparams.yaml',
         map_location=None
     )