Simple-smartsheet

* Export sheets and rows as pandas dataframe and series respectively. 22
Install the package with pandas as extras: `pip install simple-smartsheet[pandas]`
* Add multi picklist support 28
* Do not crash when deleting many rows 25
* All crud methods directly on the `Sheet` object were removed, use `SheetCrud` methods instead, e.g. `smartsheet.sheets.add_rows`

* Add a more specific constraint to marshmallow dependency (Fix 18)

* Fetch more than 100 rows in a report (Fix 19)

* Add exception `SmartsheetObjectNotFound`
* Do not crash when an unknown field is encountered from API request
* Add new summary attributes to sheet and report schema 17 introduced by this feature <https://help.smartsheet.com/learning-track/smartsheet-intermediate/sheet-summary>
* Fix several bugs in some asyncio coroutines which were not awaited
* Add a number of integration tests against Smartsheet Developer sandbox
* [Deprecated] SheetCrud methods `add_row`, `add_rows`, `update_row`, `update_rows`, `delete_row`, `delete_rows` as well as their async counterparts now have `sheet_id: int` as a first argument instead of `sheet: Sheet` object. Deprecation warning is raised if you pass `Sheet` object as the first argument. `sort_rows` still uses `sheet` object as the first argument.
* [Backwards incompatible] [Result object](https://smartsheet-platform.github.io/api-docs/result-object) now converts the received object data into an object itself. It is accessible via `result.obj` or property `result.result` which points to the same attribute. This is important in some cases, e.g. new sheet creation: `result = smartsheet.sheets.create(new_sheet_skeleton)`. `result.obj` will contain a new `Sheet`, while `result.obj.id` will have an ID of a new sheet.

* Add asyncio support, check readme and `examples/async.py` for more details
* \[Deprecated\] All methods on Sheet object, which do API call, like `add_rows`, `update_rows`, `delete_rows`, `sort_rows`, they are now available under `smartsheet.sheets` and the first argument is sheet object

* Add support for Report objects
* \[Backwards incompatible\] Change the way indexes are handled, `build_index` method should be used on Sheet or Report objects
* Unchecked checkboxes return False instead of None (12)