allow to specify all cols read as character

[vojtechhuser]

when reading a given dataset, one column has significant zeros in front of numbers.

e.g., 1 vs 0001

Current read.socrata() does not allow to force parsing all cols as characters.

something like dplyr read_csv(xxxxxx, col_types = cols(.default = "c") )

[tomschenkjr]

For linking conversations, this request has been raised on StackOverflow.