refactor(headers): export all headers and utils directly under header

Currently headers are exported at many places. For example you can access
`Transfer-Encoding` header at `header`, `header::common` and
`header::common::transfer_encoding`. Per discussion on IRC with
@seanmonstar and @reem, all contents of headers will be exposed at `header`
directly. Parsing utilities will be exposed at `header::parsing`. Header
macros can now be used from other crates.

This breaks much code using headers. It should use everything it needs
directly from `header::`, encodings are exposed at `header::Encoding::`,
connection options are exposed at `header::ConnectionOption`.

src/header/shared/mod.rs

@@ -1,26 +1,5 @@
-//! Various functions, structs and enums useful for many headers.
-
 pub use self::encoding::Encoding;
-pub use self::encoding::Encoding::{
-    Chunked,
-    Gzip,
-    Deflate,
-    Compress,
-    Identity,
-    EncodingExt};
+pub use self::quality_item::{QualityItem, qitem};
 
-pub use self::quality_item::QualityItem;
-pub use self::quality_item::qitem;
-
-pub use self::time::tm_from_str;
-
-pub use self::util::{
-    from_one_raw_str,
-    from_comma_delimited,
-    from_one_comma_delimited,
-    fmt_comma_delimited};
-
-pub mod encoding;
-pub mod quality_item;
-pub mod time;
-pub mod util;
+mod encoding;
+mod quality_item;

src/header/shared/util.rs

@@ -1,52 +0,0 @@
-//! Utility functions for Header implementations.
-
-use std::str;
-use std::fmt;
-
-/// Reads a single raw string when parsing a header
-pub fn from_one_raw_str<T: str::FromStr>(raw: &[Vec<u8>]) -> Option<T> {
-    if raw.len() != 1 {
-        return None;
-    }
-    // we JUST checked that raw.len() == 1, so raw[0] WILL exist.
-    match str::from_utf8(&raw[0][]) {
-        Ok(s) => str::FromStr::from_str(s),
-        Err(_) => None
-    }
-}
-
-/// Reads a comma-delimited raw header into a Vec.
-#[inline]
-pub fn from_comma_delimited<T: str::FromStr>(raw: &[Vec<u8>]) -> Option<Vec<T>> {
-    if raw.len() != 1 {
-        return None;
-    }
-    // we JUST checked that raw.len() == 1, so raw[0] WILL exist.
-    from_one_comma_delimited(&raw[0][])
-}
-
-/// Reads a comma-delimited raw string into a Vec.
-pub fn from_one_comma_delimited<T: str::FromStr>(raw: &[u8]) -> Option<Vec<T>> {
-    match str::from_utf8(raw) {
-        Ok(s) => {
-            Some(s.as_slice()
-                 .split(',')
-                 .map(|x| x.trim())
-                 .filter_map(str::FromStr::from_str)
-                 .collect())
-        }
-        Err(_) => None
-    }
-}
-
-/// Format an array into a comma-delimited string.
-pub fn fmt_comma_delimited<T: fmt::String>(fmt: &mut fmt::Formatter, parts: &[T]) -> fmt::Result {
-    let last = parts.len() - 1;
-    for (i, part) in parts.iter().enumerate() {
-        try!(write!(fmt, "{}", part));
-        if i < last {
-            try!(write!(fmt, ", "));
-        }
-    }
-    Ok(())
-}