feat(lib): remove extern Url type usage

BREAKING CHANGE: The `Url` type is no longer used. Any instance in the
  `Client` API has had it replaced with `hyper::Uri`.

  This also means `Error::Uri` has changed types to
  `hyper::error::UriError`.

  The type `hyper::header::parsing::HTTP_VALUE` has been made private,
  as an implementation detail. The function `http_percent_encoding`
  should be used instead.

src/http/h1/parse.rs

@@ -61,7 +61,7 @@ impl Http1Transaction for ServerTransaction {
         let path = unsafe { ByteStr::from_utf8_unchecked(path) };
         let subject = RequestLine(
             method,
-            try!(::uri::from_mem_str(path)),
+            try!(::uri::from_byte_str(path)),
         );
 
         headers.extend(HeadersAsBytesIter {

src/http/str.rs

@@ -1,8 +1,9 @@
+use std::ops::Deref;
 use std::str;
 
 use bytes::Bytes;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct ByteStr(Bytes);
 
 impl ByteStr {
@@ -10,7 +11,35 @@ impl ByteStr {
         ByteStr(slice)
     }
 
+    pub fn from_static(s: &'static str) -> ByteStr {
+        ByteStr(Bytes::from_static(s.as_bytes()))
+    }
+
+    pub fn slice(&self, from: usize, to: usize) -> ByteStr {
+        assert!(self.as_str().is_char_boundary(from));
+        assert!(self.as_str().is_char_boundary(to));
+        ByteStr(self.0.slice(from, to))
+    }
+
+    pub fn slice_to(&self, idx: usize) -> ByteStr {
+        assert!(self.as_str().is_char_boundary(idx));
+        ByteStr(self.0.slice_to(idx))
+    }
+
     pub fn as_str(&self) -> &str {
         unsafe { str::from_utf8_unchecked(self.0.as_ref()) }
     }
 }
+
+impl Deref for ByteStr {
+    type Target = str;
+    fn deref(&self) -> &str {
+        self.as_str()
+    }
+}
+
+impl<'a> From<&'a str> for ByteStr {
+    fn from(s: &'a str) -> ByteStr {
+        ByteStr(Bytes::from(s))
+    }
+}