UIManager warning when using seekTo method

[manzoorwanijk]

Due to #131, I decided to hide the default controls and create my own using slider, like this:

But, when I change the slider value and set the video position using `seekTo()`, it generates the warning, Accessing view manager configs directly off UIManager via UIManager['ReactYouTube'] is no longer supported. Use UIManager.getViewManagerConfig('ReactYouTube') instead.

Here is the screenshot of the error:

After Googling, I found two similar issues with other components - here and here

[sanjaypojo]

Facing the same issue!

[davidohayon669]

@manzoorwanijk 56c037c