adding percent sign (%) as a valid character within a hashable.format 'w...

I was running into issues storing file names with spaces in the hash object.  Although the filename is url-encoded correctly with `%20`'s, the pattern used by hashable.format to what comprimises a `word` doesn't include a percent sign as a valid character.  The hash will then revert to the default hash, as designed.

This (simple!) change fixes this.