Great-expectations

* Improve CLI help and set CLI return value to the number of unmet expectations
* Add error handling for empty columns to SqlAlchemyDataset, and associated tests
* Fix broken support for older pandas versions (346)
* Fix pandas deepcopy issue (342)

* Improve type lists in expect_column_type_to_be[_in_list] (thanks smontanaro and ccnobbli)
* Update cli to use entry_points for conda compatibility, and add version option to cli
* Remove extraneous development dependency to airflow
* Address SQlAlchemy warnings in median computation
* Improve glossary in documentation
* Add 'statistics' section to validation report with overall validation results (thanks sotte)
* Add support for parameterized expectations
* Improve support for custom expectations with better error messages (thanks syk0saje)
* Implement expect_column_value_lenghts_to_[be_between|equal] for SQAlchemy (thanks ccnobbli)
* Fix PandasDataset subclasses to inherit child class

* Fix bugs in expect_column_values_to_[not]_be_null: computing unexpected value percentages and handling all-null (thanks ccnobbli)
* Support mysql use of Decimal type (thanks bouke-nederstigt)
* Add new expectation expect_column_values_to_not_match_regex_list.
* Change behavior of expect_column_values_to_match_regex_list to use python re.findall in PandasDataset, relaxing matching of individuals expressions to allow matches anywhere in the string.
* Fix documentation errors and other small errors (thanks roblim, ccnobbli)

Corrects failure to include new data_context module in source distribution.

Welcome to Great Expectations version 0.4.0! Please note that this release includes several major breaking API changes. Please see the changelog below for more information!

v.0.4.0
-------
* Initial implementation of data context API and SqlAlchemyDataset including implementations of the following expectations:
* expect_column_to_exist
* expect_table_row_count_to_be
* expect_table_row_count_to_be_between
* expect_column_values_to_not_be_null
* expect_column_values_to_be_null
* expect_column_values_to_be_in_set
* expect_column_values_to_be_between
* expect_column_mean_to_be
* expect_column_min_to_be
* expect_column_max_to_be
* expect_column_sum_to_be
* expect_column_unique_value_count_to_be_between
* expect_column_proportion_of_unique_values_to_be_between
* Major refactor of output_format to new result_format parameter. See docs for full details.
* exception_list and related uses of the term exception have been renamed to unexpected
* the output formats are explicitly hierarchical now, with BOOLEAN_ONLY < BASIC < SUMMARY < COMPLETE. `column_aggregate_expectation`s now return element count and related information included at the BASIC level or higher.
* New expectation available for parameterized distributions--expect_column_parameterized_distribution_ks_test_p_value_to_be_greater_than (what a name! :) -- (thanks ccnobbli)
* ge.from_pandas() utility (thanks schrockn)
* Pandas operations on a PandasDataset now return another PandasDataset (thanks dlwhite5)
* expect_column_to_exist now takes a column_index parameter to specify column order (thanks louispotok)
* Top-level validate option (ge.validate())
* ge.read_json() helper (thanks rjurney)
* Behind-the-scenes improvements to testing framework to ensure parity across data contexts.
* Documentation improvements, bug-fixes, and internal api improvements