Iotoolz

- Fix typo for HttpStream: schemes -> schemas
- key for S3Stream should not have leading slash

- Fix bug where dynamic mock stream class is improperly created when the required dependencies are not available.

- Add extension `iotoolz.extensions.s3.S3Stream` which is implemented with `boto3`.

- Converted sphinx docs to mkdocs for better look and feel.
- Removed the need for a context manager for the iterable.
- Renamed the 2 abstract methods.

- Initial Release

- Features:
- `iotoolz.AbcStream` is an abstract class to represent any IO. It follows the `open` very closely.