How to drawSVG in a dom

This plugin is awesome, thanks to contributors.
I want to write a `markdown-it` plugin support for flowchart,
and i need to drawSVG in a dom like this:
`javascript`:
```javascript
var FlowChart = require('flowchart.js');
var diagram = FlowChart.parse(
"st=>start: Start:>http://www.google.com[blank]\n"+
"e=>end:>http://www.google.com\n"+
"op1=>operation: My Operation\n" +
"sub1=>subroutine: My Subroutine\n" +
"cond=>condition: Yes\n" +
"or No?:>http://www.google.com\n" +
"io=>inputoutput: catch something...\n" +
"\n" +
"st->op1->cond\n" +
"cond(yes)->io->e\n" +
"cond(no)->sub1(right)->op1\n"
);
var dom = document.createElement('div');
diagram.drawSVG(dom);
// document.appendChild(dom);
var _dia = document.getElementById('diagram');
_dia.appendChild(dom);
```
`html`:
```html

```
but it cause some problem
1. The size of box not correct:
2. The console show me that:

I have no idea how to fix it, help please.
Thanks for your time.
I am a chinease, sorry about for my english.

Start by reproducing the provided browser example using FlowChart.parse and diagram.drawSVG(dom), then inspect the two reported symptoms: incorrect box sizing and the console message. Compare the result with the expected diagram in the attached images; done means the SVG renders with correct box dimensions and without the reported console problem.

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