* 🐛 keep the empty dictionary though it looks useless but charts needs them. fix#555
* 👕 keep empty array too. update 📖
* 🎨 minor tweaks on the source code
* Update: pink test folder
* Update: changelog update
* 🐛 fix theme color problem for themes other than dark, #544
* 🔬 test remove_key_with_none_value and whitening
* 📚 update docs and pump version
* Update json_serializable.py
* Update __init__.py
* 💚 fix unit test failures
* 🔥 get rid of dev code
* 💚 pass all unit tests
* 👕 use python 2 to generate the fixtures
* 🔥 remove empty dictionary that resulted from cleaning
* 🔬 more test cases. 👕 whitening
* 💚 ignore basestring please, flake8
* 🔨 code refactor test
* 🔨 address review feedbacks
* 💄 change single quote
* Update: docs update
* Update: img link update
* Update: docs update
* 🐛 turn on split line for scatter diagram. fix#516
* 🔥 remove documentation that echos the function name
* ✨ support dark theme. fix#512
* ✨ support global_theme in configure function. improves #512
* ✨ use_theme, related to #512
* ✨ support 5 more external themes which come from echarts-themes-pypkg and echarts-themes-js, #512
* 📰 add missing test fixtures
* 💚 make unit test pass
* 📚 document themes usage
* 📚 add cross reference
* 📚 update change log and pump version
* Update: update some docs
* Update: typo fixed
* Update: prepare docs update
* Update: 鉴于现在 md 做 long description 效果不佳，转化为 rst 又出现问题，所以暂时取消
* Fix: fixed broken test, remove unused codecs
