Bumping up version to 1.18.0 for horovod release (aws#604)

* Bumping up version to 1.18.0 for horovod release

Support of Horovod and TF 1.12 for TensorFlow Script Mode. TFS 1.12 s…

…upport (aws#567)

* Support of Horovod and TF 1.12 for TensorFlow Script Mode

Support VPC config for hyperparameter tuning and bump version to 1.17…

….2 (aws#598)

Supporting inter-container traffic encryption flag (aws#595)

Upgrade version to 1.17.0 (aws#592)

Upgrade version to 1.16.3 (aws#564)

Add support for Hyperparameter Tuning Early Stopping (aws#550)

Update version to 1.16.1.post1 (aws#516)

update sdk for new re:invent 2018 features

fix FileNotFoundError for entry_point without source_dir (aws#510)

* fix FileNotFoundError when user provides an entry_point but no source_dir

* update docstring

* bump version to 1.15.2

* fix integ tests failing due to breaking ExecuteUserScriptError change