Add Default implementation for ArrayString

Fixes #67.

src/array_string.rs

@@ -31,6 +31,12 @@ pub struct ArrayString<A: Array<Item=u8>> {
     len: A::Index,
 }
 
+impl<A: Array<Item=u8>> Default for ArrayString<A> {
+    fn default() -> ArrayString<A> {
+        ArrayString::new()
+    }
+}
+
 impl<A: Array<Item=u8>> ArrayString<A> {
     /// Create a new empty `ArrayString`.
     ///

tests/tests.rs

@@ -456,3 +456,13 @@ fn test_sizes() {
     let v = ArrayVec::from([0u8; 1 << 16]);
     assert_eq!(vec![0u8; v.len()], &v[..]);
 }
+
+#[test]
+fn test_default() {
+    use std::net;
+    let s: ArrayString<[u8; 4]> = Default::default();
+    // Something without `Default` implementation.
+    let v: ArrayVec<[net::TcpStream; 4]> = Default::default();
+    assert_eq!(s.len(), 0);
+    assert_eq!(v.len(), 0);
+}