perf(http): changes http parsing to use httparse crate

httparse is a http1 stateless push parser. This not only speeds up
parsing right now with sync io, but will also be useful for when we get
async io, since it's push based instead of pull.

BREAKING CHANGE: Several public functions and types in the `http` module
  have been removed. They have been replaced with 2 methods that handle
  all of the http1 parsing.

src/method.rs

@@ -2,6 +2,7 @@
 use std::fmt;
 use std::str::FromStr;
 
+use error::HttpError;
 use self::Method::{Options, Get, Post, Put, Delete, Head, Trace, Connect, Patch,
                    Extension};
 
@@ -68,10 +69,10 @@ impl Method {
 }
 
 impl FromStr for Method {
-    type Err = ();
-    fn from_str(s: &str) -> Result<Method, ()> {
+    type Err = HttpError;
+    fn from_str(s: &str) -> Result<Method, HttpError> {
         if s == "" {
-            Err(())
+            Err(HttpError::HttpMethodError)
         } else {
             Ok(match s {
                 "OPTIONS" => Options,