Fix for parsing scientific notation

Hello,

Inkscape svg output sometimes contains floats in "scientific notation" (e.g. 5e-3), which the svg standard seems to support? I just made a quick patch to the code that "protects" such floats during tokenization. A (rather long -- sorry) test case is also included. You may want to either pull the changes, or refine your own fix.

Many thanks for sharing this library!

George & Rebecca