Datalab

Feature
- Modify variable async to async_ in utils to avoid reserved keyword clash. Allows use for Python 3.5+ (728)

Documentations
- Fixes documentation urls. (719)

Dependencies
- Bump pillow from 3.4.1 to 6.2.0 in /solutionbox/ml_workbench/xgboost (726)
- Bump pillow from 3.4.1 to 6.2.0 in /solutionbox/ml_workbench/tensorflow (721)
- Bump pillow from 3.4.1 to 6.2.0 in /solutionbox/image_classification (729)
- Bump tensorflow from 1.8.0 to 1.15.2 in /solutionbox/ml_workbench/tensorflow (726
- Bump tensorflow from 1.8.0 to 1.15.2 in /solutionbox/ml_workbench/xgboost (727)

First release after GA brings a few bug fixes:
- Fix subquery order dependency in Query constructor (https://github.com/googledatalab/pydatalab/commit/469da4b5de35832f3ebf5635315d4228250f5806)
- Fix a bug where an unbounded number of credentials wrappers got added (https://github.com/googledatalab/pydatalab/commit/84ccb95f88a307e1a730b0395db9a7d3f2fdb758)
- Fix a bug where `%bq query` table view is broke (https://github.com/googledatalab/pydatalab/commit/035a4a5a0abd17826e0af62b4cbfe87e21d5f771)
- Fix Query.data_sources method to return dict instead of list of tuples (https://github.com/googledatalab/pydatalab/commit/9d79da7a85d809847be8430066e90749fadb8916)
- Fixes for Python3 compatibility (https://github.com/googledatalab/pydatalab/commit/5deca12bf8bc6843a25d8ce147a4932ec5d102c5, https://github.com/googledatalab/pydatalab/commit/b27dc582882fe5497af49d45fc28204e4c46db12, and https://github.com/googledatalab/pydatalab/commit/99ec4491d5188a12d4a118168c84b2a45d504d85)

This is the GA release of the Google Datalab libraries. It's also on [PyPI](https://pypi.python.org/pypi/datalab), so you can get install it using pip:

pip install datalab


Migration Guide to migrate from previous datalab releases to the GA release:
https://github.com/googledatalab/pydatalab/wiki/%60datalab%60-to-%60google.datalab%60-Migration-Guide