Inkslide chokes on paths with spaces

[EmilyDirsh]

If you're running inkslide against a folder in a path with spaces, inkslide passes it incorrectly to inkscape which interprets it as passing multiple files which don't exist.

For example, I tried running inkslide ~/My\ Slides/test.svg and got error messages like the following:

** (inkscape:24920): WARNING **: Specified document /home/emily/My cannot be opened (does not exist or not a valid SVG file)
** (inkscape:24920): WARNING **: Specified document Slides/test.svg cannot be opened (does not exist or not a valid SVG file)