[FIX] Curl#urlalize - CGI.escape for param values

- URI.escape does not escapes characters '&' and '?'. When in parameter
  value is one of this characters, things goes seriously wrong.
  For example: urlalize('http://foo.bar', a: 'b&c?d=1')
               => "http://foo.bar?a=b&c?d=1"
  As you can see, this is definitely wrong url.
  But it is even worse. When I escape my value with CGI.escape,
  URI.escape in urlalize escapes all '%'. So again, wrong :(
  Example: urlalize('http://foo.bar', a: CGI.escape('b&c'))
           => 'http://foo.bar?a=b%2526c'

  I don't see any way how to send '&' or '?' to server. In first case,
  parameter value with '&' or '?' is separated into more values in
  second case, for '&' will be send '%2526' which server represents as
  '%26' instead of '&'.

- solution: use CGI.escape for values instead of URI.escape