Use Cmd(::Vector{String}) to make curl Cmd

[david-macmahon]

This avoids having to quote strings that may contain embedded spaces (e.g. the query string), which can cause problems on some systems if those surrending quotes are not removed from the query.

[david-macmahon]

Not sure about this PR. I think the quoting conventions (requirements?) of different curl versions may have the potential to be problematic either with or without the quotes. With the quotes is problematic for at least one curl version (7.47.0), but not problematic for 7.61.1. Without the quotes works for simple queries on both of those curl versions, but not sure it will work with more complex queries that happen to contain "curl-special" characters (e.g. quotes and semicolons). I think switching to HTTP.jl is the way to go. I'll probably open a different PR for the HTTP.jl solution and close this one at that time.

[david-macmahon]

Closing this PR because #2 fixes the same issue in a better (IMHO) way.