expose this as a npm package

[hanzhangyu]

Dear @skorunka , I had export this to a npm package.
And fixed two bugs in the tree algorithm.

Fixed:

1. x may less than zero
   https://jsfiddle.net/PaulHan/xhLatwg1/1/
2. the sibling's has an error order
   https://jsfiddle.net/PaulHan/qovht6y7/

Feature:

1. support toggle
2. support tooltip and format
3. support padding and border
4. support chart auto-size

Todo:

Let user select destroy the element or not. if not, we will calculate the diff and use animate to update the node.

[skorunka]

Hi @hanzhangyu I'm no longer working on this. I have added you as a collaborator, so you can freely integrate the bug-fixes and new features. Thank you. F