symbolic-taylor-series can't take perturbations as arguments

[sritchie]

For example:

((D (fn [x] (first (symbolic-taylor-series exp x)))) 10)
;;=> 0

What's happening:

• x is getting substituted for a symbol, say x0
• this is replacing the Dual, not doing the substitition inside of the primal
• so (exp x0) pops out, and the literal implementation doesn't recurse into its lists, because in NORMAL generic arithmetic without the subs, (exp <dual>) would return type dual, not type literal

So we can fix typical-object here or do something in the function body...