SVG height and width
I'm using react-primitives-svg to render the same SVG code to both web and sketch:

```
switch (Platform.OS) {
  case "sketch":
    SvgLib = require("react-primitives-svg/lib/core.sketch");
    break;
  case "web":
    SvgLib = require("react-primitives-svg/lib/core.web");
    break;
  default: // React Native should be able to pick up `core.ios.js` or `core.android.js` according to the platform
    // SvgLib = require("react-primitives-svg");
}
```

Now the SVG height and width seem to be interpreted differently for Sketch and web.
`<Svg viewBox="0 0 200 200" width="200" height="200">` is more like 20/20 on web, but OK in Sketch.
but...
`<Svg viewBox="0 0 200 200">` renders 95.61px /.47px in Sketch, but OK on web.

So I can't use the same code.

@alampros suggests it maybe a yoga layout issue as he had a similar problem #204 