Is there a way to use a character vector of column names?

```
library(dplyr)
library(tidyverse)
# works
x <- c(quo(a), quo(b))
tibble(a=c(1,2,2,3), b=c(1,2,2,3), c=1:4) %>% count(!!!x)
#> # A tibble: 3 x 3
#> a b n
#> <dbl> <dbl> <int>
#> 1 1 1 1
#> 2 2 2 2
#> 3 3 3 1
# doesn't work
x <- c("a", "b")
tibble(a=c(1,2,2,3), b=c(1,2,2,3), c=1:4) %>% count(!!!x)
#> # A tibble: 1 x 3
#> `"a"` `"b"` n
#> <chr> <chr> <int>
#> 1 a b 4
```

Created on 2018-11-21 by the reprex package (v0.2.0).