Remove kiva.fonttools.sstruct

[jwiggins]

I can't find any code which actually uses the kiva.fonttools.sstruct module. It should probably be removed.

[rahulporuri]

I did a GitHub wide search for "kiva.fonttools.sstruct" and there are no actual uses of that module on GitHub - https://github.com/search?q=%22kiva.fonttools.sstruct%22&type=code . I've done some code archeology and this is the first github commit where the sstruct module was added - https://github.com/enthought/enable/tree/c40a38cb216544a9da393503af47083b38f84b05 - which is how I realized that the kiva.fonttools.sstruct module was used in the vendorized fontTools code.

The vendorized fontTools code was removed in #264 - so we should now be able to remove it without any issues.

@jwiggins are you convinced enough to remove the "needs-investigation" label?