Kaleido

Overview
This is the first public pre-release of the Kaleido executable and PyPI package

Added
- Support updating scope properties after construction. Automatically restart kaleido executable if required
- Add `default_format`, `default_width`, `default_height`, and `default_scale` scope properties to control defaults of `to_image` method

Updated
- Refactor linux build scripts to be consistent with mac and windows

Added
- Include version number in JSON response when first launching kaleido executable
- Include version number in Python package as `kaleido.__version__`.
- Generate version number from git tag
- Allow Python scopes to specify formats that should be base64 decoded into text (e.g. svg)
- Python process now silently collects standard error stream and displays this when an unknown error occurs in the kaleido executable on initialization or image export.

Fixed
- Unset `LD_PRELOAD` environment variable on Linux to support Google Colab.

First preview release!

win_toolchain
Fake release for the purpose of uploading the 1.3GB windows toolchain zip file. This is the result of the `package_from_installed.py` command described in https://chromium.googlesource.com/chromium/src.git/+/master/docs/win_cross.md