Allow destructuring in p/for

[ferdinand-beyer]

The for macro asserts that the binding form is a symbol:

(assert (symbol? sym) (str "Requires symbol for binding name: " sym))

This restriction seems unnecessary, and prevents users from using destructuring:

(p/parse (p/for [[x & xs] (p/*many char/number?)]
           (p/result {:first x, :rest xs}))
         "12345")

Maybe we can remove the assert?

[serioga]

Removed the assert :-)