Fix some clippy warnings

* Rows cannot implement iterator
* DatabaseName is passed by value => Copy ?

src/lib.rs

@@ -152,6 +152,7 @@ fn path_to_cstring(p: &Path) -> Result<CString> {
 }
 
 /// Name for a database within a SQLite connection.
+#[derive(Copy,Clone)]
 pub enum DatabaseName<'a> {
     /// The main database.
     Main,

src/row.rs

@@ -27,6 +27,7 @@ impl<'stmt> Rows<'stmt> {
     /// lifetime of the returned row is tied to the lifetime of `self`. This is a
     /// "streaming iterator". For a more natural interface, consider using `query_map`
     /// or `query_and_then` instead, which return types that implement `Iterator`.
+    #[cfg_attr(feature = "cargo-clippy", allow(should_implement_trait))] // cannot implement Iterator
     pub fn next<'a>(&'a mut self) -> Option<Result<Row<'a, 'stmt>>> {
         self.stmt
             .and_then(|stmt| match stmt.step() {