arbor_path fails when script element has no path

[emlyn]

If arbor.js is included without any explicit path, as in:

<script src="arbor.js"></script>

then the arbor_path() function incorrectly returns "/arbor.js", which doesn't work when it is not run from the root directory.
A workaround is to instead include arbor with:

<script src="./arbor.js"></script>

but perhaps arbor_path() should default to the current directory instead of the root?