Great-expectations

* Fix an issue in generated documentation where the Home button failed to return to the index
* Add S3 Generator to module docs and improve module docs formatting
* Add support for views to QueryGenerator
* Add success/failure icons to index page
* Return to uniform histogram creation during profiling to avoid large partitions for internal performance reasons

* Add an S3 generator, which will introspect a configured bucket and generate batch_kwargs from identified objects
* Add support to PandasDatasource and SparkDFDatasource for reading directly from S3
* Enhance the Site Index page in documentation so that validation results are sorted and display the newest items first when using the default run-id scheme
* Add a new utility method, `build_continuous_partition_object` which will build partition objects using the dataset API and so supports any GE backend.
* Fix an issue where columns with spaces in their names caused failures in some SqlAlchemyDataset and SparkDFDataset expectations
* Fix an issue where generated queries including null checks failed on MSSQL (695)
* Fix an issue where evaluation parameters passed in as a set instead of a list could cause JSON serialization problems for the result object (699)

* BREAKING: slack webhook URL now must be in the profiles.yml file (treat as a secret)
* Profiler improvements:
- Display candidate profiling data assets in alphabetical order
- Add columns to the expectation_suite meta during profiling to support human-readable description information
* Improve handling of optional dependencies during CLI init
* Improve documentation for create_expectations notebook
* Fix several anachronistic documentation and docstring phrases (659, 660, 668, 681; thanks StevenMMortimer)
* Fix data docs rendering issues:
- documentation rendering failure from unrecognized profiled column type (679; thanks dinedal))
- PY2 failure on encountering unicode (676)

* Standardize the way that plugin module loading works. DataContext will begin to use the new-style class and plugin identification moving forward; yml configs should specify class_name and module_name (with module_name optional for GE types). For now, it is possible to use the "type" parameter in configuration (as before).
* Add support for custom data_asset_type to all datasources
* Add support for strict_min and strict_max to inequality-based expectations to allow strict inequality checks
(thanks RoyalTS!)
* Add support for reader_method = "delta" to SparkDFDatasource
* Fix databricks generator (thanks sspitz3!)
* Improve performance of DataContext loading by moving optional import
* Fix several memory and performance issues in SparkDFDataset.
- Use only distinct value count instead of bringing values to driver
- Migrate away from UDF for set membership, nullity, and regex expectations
* Fix several UI issues in the data_documentation
- Move prescriptive dataset expectations to Overview section
- Fix broken link on Home breadcrumb
- Scroll follows navigation properly
- Improved flow for long items in value_set
- Improved testing for ValidationRenderer
- Clarify dependencies introduced in documentation sites
- Improve testing and documentation for site_builder, including run_id filter
- Fix missing header in Index page and cut-off tooltip
- Add run_id to path for validation files

* New Validation Renderer! Supports turning validation results into HTML and displays differences between the expected and the observed attributes of a dataset.
* Data Documentation sites are now fully configurable; a data context can be configured to generate multiple
sites built with different GE objects to support a variety of data documentation use cases. See data documentation guide for more detail.
* CLI now has a new top-level command, `build-documentation` that can support rendering documentation for specified sites and even named data assets in a specific site.
* Introduced DotDict and LooselyTypedDotDict classes that allow to enforce typing of dictionaries.
* Bug fixes: improved internal logic of rendering data documentation, slack notification, and CLI profile command when datasource argument was not provided.

* Fix missing requirement for pypandoc brought in from markdown support for notes rendering.