Gobbli

Output a warning when gobbli is imported if certain third-party libraries are installed that shadow first-party modules having the same name.

Fix issues with Dockerfiles not being included in wheels, meta.json missing from source distribution, and some Docker-only Python files missing.

- Ensure Dockerfiles are uploaded to PyPI via MANIFEST.in (9)
- Better error message when models are run without building first (8)

Some minor changes to docs, README, etc.

Initial public release includes the following models:

- BERT (training, prediction, embeddings)
- MT-DNN (training, prediction, embeddings)
- Universal Sentence Encoder (embeddings)
- fastText (training, prediction, embeddings)
- pytorch_transformer Transformers (training, prediction, embeddings)

Additional features include:
- Experiments (ClassificationExperiments only)
- Data augmentation (Word2Vec, WordNet, and BERTMaskedLM)
- Document windowing