ast() should print quosures specially

[hadley]

library(rlang)
library(lobstr)

q1 <- new_quosure(expr(x), env(x = 1))
q2 <- new_quosure(expr(x), env(x = 10))

lobstr::ast(!!q1 + !!q2)
#> Warning: `quo_expr()` is soft-deprecated as of rlang 0.2.0.
#> Please use `quo_squash()` instead
#> This warning is displayed once per session.
#> █─`+` 
#> ├─x 
#> └─x

^{Created on 2018-11-08 by the reprex package (v0.2.1)}

(Probably what I was thinking in #6)