[query] Add QueryError #44 (#45)

* Create query_error_test.rs

* Create query_error.rs

* Update lib.rs

src/lib.rs

@@ -1,9 +1,11 @@
 mod db;
 mod query;
+mod query_error;
 mod query_result;
 mod transaction;
 
 pub use db::Db;
 pub use query::Query;
+pub use query_error::QueryError;
 pub use query_result::QueryResult;
 pub use transaction::Transaction;

src/query_error.rs

@@ -0,0 +1,2 @@
+#[derive(Default)]
+pub struct QueryError {}

tests/query_error_test.rs

@@ -0,0 +1,6 @@
+extern crate agdb;
+
+#[test]
+fn query_error_is_public_type() {
+    let _error = agdb::QueryError::default();
+}