Adds alphanumeric sorting reader option

[mlangens]

A little clunkily written, but reliably gets the job done. Any input is welcome!

[JangoSteve]

Drop the toString() on the attr names, since names are always strings anyway regardless of using integers, etc to refer to them.

[JangoSteve]

Overall, this functionality looks good, though it's difficult to understand exactly what's going on. If you could comment each of the non-obvious lines to say briefly what they do (or maybe provide an example of a and b and how each line would return in that case).

Also, fix formatting to be a consistent 2-space indentation throughout the method.