Rename `LuaTable::has` to `contains_key`

This is what all Rust maps use

src/lua.rs

@@ -233,7 +233,7 @@ impl<'lua> LuaTable<'lua> {
     }
 
     /// Checks whether the table contains a non-nil value for `key`.
-    pub fn has<K: ToLua<'lua>>(&self, key: K) -> LuaResult<bool> {
+    pub fn contains_key<K: ToLua<'lua>>(&self, key: K) -> LuaResult<bool> {
         let lua = self.0.lua;
         let key = key.to_lua(lua)?;
         unsafe {

src/tests.rs

@@ -40,7 +40,7 @@ fn test_load() {
         "#,
         None,
     ).unwrap();
-    assert!(module.has("func").unwrap());
+    assert!(module.contains_key("func").unwrap());
     assert_eq!(
         module
             .get::<_, LuaFunction>("func")