Clean up test code.
Add some inline SVG tests for embedded PNGs and SVGs.
Abstract inline SVG tests.
Add an SVG rendering sandbox to test page.
Throw error when an image on external host is detected.
Handle multiple sandbox renders and fix logic error when detecting external images.
When there's an error, hide the sandbox's preview.
Bring render button back home.
Improve scaling by making it dramatically simpler.

- Add test for scaling an SVG.
- Use viewBox for scaling SVG (see https://github.com/poptip/saveSvgAsPng/commit/a93874389411cb5b6db4f1e27832ab1321381469).
- Remove scaling group element.
- Remove moving of children from one parent node to another (hopefully helps with #5, #6, and #7).
Fix check for external images.
Add some explanation to test page. Move sandbox to top.
Handle errors caused by unrecognized CSS selectors.
Don't filter out CSS rules that are not used by the SVG.

Angular uses CSS selectors that Element.querySelectorAll does not recognize (specifically namespaced attribute names). Since the SVG is being converted to a PNG, there isn't much reason to reduce the size of the SVG before exporting.

Fixes #11.
fixes a NaN parse error 

if width or height are postfixed with "px" for example, like width="400px", then the parseInt results in a NaN. This fixes that issue.
Handle sizing of output SVG when original SVG is sized by CSS.
Add additional test case to check for px used in width and height attributes.
Add null check for rules in styles function

I had an issue similar to #7. When trying to save a Google Chart, I encountered the same error "Cannot read property 'length' of null", also in Chrome. Added a null check to prevent this from occurring.
Merge pull request #16 from trhall/gh-pages

Add null check for rules in styles function
Ignore styles on foreign hosts.

Fixes #17.

- Add test page stylesheet link to foreign host to test failure under Firefox.
- Refactor external URL check into isExternal function.
- Warn instead of throwing an error when trying to embed images from foreign hosts.
- Warn when trying to get styles from foreign hosts.
Merge branch 'gh-pages' of github.com:exupero/saveSvgAsPng into gh-pages