Redivis

Fixed a bug where the upload of very large strings wasn't handled properly, causing `413 Request Entity Too Large` errors. Strings should now be handled the same as other data inputs to uploads.

- All `list_rows()` methods now return a list of instances of the custom `Row` class, rather than named tuples. This works around an issue with named tuples in that their keys cannot start with an underscore character (e.g., `_var1`), partially resolving 29
- In practice, the behavior and usage should be the same as before. You can access values in each row by position (index) -> `row[0]`, by key like a dict -> `row['_var1']`, or as properties -> `row._var1`

Fix query.to_dataframe throws for empty results 28

Full reference available at: https://apidocs.redivis.com/client-libraries/redivis-python/reference

Breaking changes
- Previously, when multiple uploads on a version of a table had the same name, this library would accept these duplicate uploads by automatically appending a counter to the name of subsequent uploads. With this latest version, the default behavior is to raise an error when multiple uploads have the same name, under the assumption that the intent probably isn't to upload the same file twice.
- See the `rename_on_conflict`, `replace_on_conflict`, and `if_exists` parameters on the [upload.create method](https://apidocs.redivis.com/client-libraries/redivis-python/reference/upload#create-data-type-delimited-delimiter-none-schema-none-has_header_row-true-skip_bad_records-false-all) to control this behavior.

New features
- Add support for creating index tables via `table.create(is_file_index = True)` [(docs)](https://apidocs.redivis.com/client-libraries/redivis-python/reference/table#create-description-none-upload_merge_strategy-append-is_file_index-false)
- Add support for uploading non-tabular files to an index table via `table.add_file(name, data)` [(docs)](https://apidocs.redivis.com/client-libraries/redivis-python/reference/table#add_file-name-data)
- Several new parameters on the `upload.create() method` [(docs)](https://apidocs.redivis.com/client-libraries/redivis-python/reference/upload#create-data-type-delimited-delimiter-none-schema-none-has_header_row-true-skip_bad_records-false-all)
- `allow_jagged_rows`
- `rename_on_conflict`
- `replace_on_conflict`
- `metadata`: specify variable labels, descriptions, and valueLabels as part of the upload
- Add `variable.update(label, description, value_labels)` method to update variable metadata [(docs)](https://apidocs.redivis.com/client-libraries/redivis-python/reference/variable#update-label-description-value_labels)

Bug fixes
- Fixed an issue with multipart file uploads, which could have led to some of the `upload.create` parameters being ignored in certain situations.