Added support for SVGZ (i.e. GZIPed SVG).

Hello,

I forked your svg-android project and added support for SVGZ files (i.e. GZIPed SVGs). The requires only a small amount of code added in SVGBuilder.
I've based this on work by josefpavlik (https://github.com/josefpavlik/svg-android/commit/fc0522b2e1). However I made an improvement by decorating the InputStream with a BufferedInputStream when mark/reset are not supported. Josef's version failed in some cases because of that reason.

I hope you'll merge this in your project such that maven users can start using this.

Best,

Matthias