dark theme support

Please add support for dark theme:
![image](https://user-images.githubusercontent.com/14617699/69095651-d502ec00-0a63-11ea-9fed-98f9c921b325.png)
![image](https://user-images.githubusercontent.com/14617699/69095916-5e1a2300-0a64-11ea-9a5a-26d08388a121.png)
![image](https://user-images.githubusercontent.com/14617699/69096015-99b4ed00-0a64-11ea-8566-becd6fb0a126.png)