metadata fails on HTTP.URI

[dgleich]

The following code succeeds:

using FileIO, HTTP
img = load(HTTP.URI("https://github.com/JuliaLang/julia-logo-graphics/raw/master/images/julia-logo-color.png"))
mdata = metadata(download("https://github.com/JuliaLang/julia-logo-graphics/raw/master/images/julia-logo-color.png"))

but these codes fail:

mdata = metadata(HTTP.URI("https://github.com/JuliaLang/julia-logo-graphics/raw/master/images/julia-logo-color.png"))

The solution is to add a metadata function to the HTTP override.