funk: Warn on spaces in filenames

[mcandre]

Spaces in filenames present a tremendous, unnecessary burden on code manipulating these files. Everything from POSIX sh, to UNIX find, to xargs, makefiles, and tab completion gets screwy on spaces.

• [ ] So let's have funk warn when a filename features an ASCII space.
• [ ] In fact, if the directory path housing the script has a space, that's just as bad.