Remove Encodable/Decodable support for unstable types

When `Box<[T]>` and `VecMap` are `#[stable]` to construct the implementations
can be added back, but the goal is currently for this crate to build on stable
rust so they are going to be removed for now.

Author: alexcrichton

src/collection_impls.rs

@@ -13,7 +13,7 @@
 use std::hash::Hash;
 
 use {Decodable, Encodable, Decoder, Encoder};
-use std::collections::{LinkedList, VecDeque, BTreeMap, BTreeSet, HashMap, HashSet, VecMap};
+use std::collections::{LinkedList, VecDeque, BTreeMap, BTreeSet, HashMap, HashSet};
 
 impl<
     T: Encodable
@@ -184,28 +184,3 @@ impl<T> Decodable for HashSet<T> where T: Decodable + Hash + Eq, {
         })
     }
 }
-impl<V: Encodable> Encodable for VecMap<V> {
-    fn encode<S: Encoder>(&self, e: &mut S) -> Result<(), S::Error> {
-        e.emit_map(self.len(), |e| {
-                for (i, (key, val)) in self.iter().enumerate() {
-                    try!(e.emit_map_elt_key(i, |e| key.encode(e)));
-                    try!(e.emit_map_elt_val(i, |e| val.encode(e)));
-                }
-                Ok(())
-            })
-    }
-}
-
-impl<V: Decodable> Decodable for VecMap<V> {
-    fn decode<D: Decoder>(d: &mut D) -> Result<VecMap<V>, D::Error> {
-        d.read_map(|d, len| {
-            let mut map = VecMap::new();
-            for i in 0..len {
-                let key = try!(d.read_map_elt_key(i, |d| Decodable::decode(d)));
-                let val = try!(d.read_map_elt_val(i, |d| Decodable::decode(d)));
-                map.insert(key, val);
-            }
-            Ok(map)
-        })
-    }
-}

src/serialize.rs

@@ -415,13 +415,6 @@ impl< T: Decodable> Decodable for Box<T> {
     }
 }
 
-impl< T: Decodable> Decodable for Box<[T]> {
-    fn decode<D: Decoder>(d: &mut D) -> Result<Box<[T]>, D::Error> {
-        let v: Vec<T> = try!(Decodable::decode(d));
-        Ok(v.into_boxed_slice())
-    }
-}
-
 impl<T:Encodable> Encodable for Rc<T> {
     #[inline]
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {