Sanitize startpage path with $sanitizer->path()

For sanitizing paths $sanitizer->path() is obviously preferred solution
over $sanitizer->selectorValue(). In addition to that future changes to
selectorValue() may cause problems when trying to sanitize a path to be
used as whole selector instead of individual selector value.
Merge pull request #10 from teppokoivula/master

Sanitize startpage path with $sanitizer->path()