I realized that `params.Del("SkipTLSVerify")` doesn't have any
effect because keys are always lowercased. So it should really
be `params.Del("skiptlsverify")`.
There's also a little bug introduced by 3bf52aa and b1d1248: if
one passes `ProgressWriter` object having `Stringer` interface
i.e. `bytes.Buffer` it ends up been serialized in query with
`util.ToParams()`.
To circumvent both problems I propose to mark non-serializable
parameters with `schema:"-"` so there's no need to delete them from
resulting `url.Values`.
Signed-off-by: Vladimir Kochnev <hashtable@yandex.ru>
cfdca82938