feat(headers): add Range header

src/header/common/mod.rs

@@ -40,6 +40,7 @@ pub use self::if_range::IfRange;
 pub use self::last_modified::LastModified;
 pub use self::location::Location;
 pub use self::pragma::Pragma;
+pub use self::range::{Range, RangeSpec};
 pub use self::referer::Referer;
 pub use self::server::Server;
 pub use self::set_cookie::SetCookie;
@@ -349,6 +350,7 @@ mod if_unmodified_since;
 mod last_modified;
 mod location;
 mod pragma;
+mod range;
 mod referer;
 mod server;
 mod set_cookie;