Phantom render bug

Hi @garris , i found that screenshots with phantom engine is a broken little bit and i`m ot sure is it some issue with backstop, casper or phantomjs. Maybe you know why it happens or can suggest vector for me how to understood where the problem is.
Step to reproduce
1. Create new folder and open it in cmd
2. Run ``backstop init``
3. Change engine to 'phantom' (btw i didn`t find which variant preferable 'phantomjs' or phantom because i see two different variant in examples)
4. Remove scripts fron onReady and onBefore(in other case it didn`t works)
5. Run ``backstop test``
6. Look into screenshots (textes are no aligned and some empty spaces whick are not present when you will open this page)
backstop.json
```
{
"id": "backstop_default",
"viewports": [
{
"label": "phone",
"width": 320,
"height": 480
},
{
"label": "tablet",
"width": 1024,
"height": 768
}
],
"scenarios": [
{
"label": "BackstopJS Homepage",
"cookiePath": "backstop_data/engine_scripts/cookies.json",
"url": "https://garris.github.io/BackstopJS/",
"referenceUrl": "",
"readyEvent": "",
"readySelector": "",
"delay": 0,
"hideSelectors": [],
"removeSelectors": [],
"hoverSelector": "",
"clickSelector": "",
"postInteractionWait": "",
"selectors": [],
"selectorExpansion": true,
"misMatchThreshold" : 0.1,
"requireSameDimensions": true
}
],
"paths": {
"bitmaps_reference": "backstop_data/bitmaps_reference",
"bitmaps_test": "backstop_data/bitmaps_test",
"engine_scripts": "backstop_data/engine_scripts",
"html_report": "backstop_data/html_report",
"ci_report": "backstop_data/ci_report"
},
"report": ["browser"],
"engine": "phantomjs",
"engineFlags": [],
"asyncCaptureLimit": 5,
"asyncCompareLimit": 50,
"debug": false,
"debugWindow": false
}
```
And screenshots (text and image are not centerd and some empty space at right part of screen)