[query] Add Transaction #35 (#36)

* Create transaction_test.rs

* Create transaction.rs

* Update lib.rs

src/lib.rs

@@ -1,7 +1,9 @@
 mod db;
 mod query;
 mod query_result;
+mod transaction;
 
 pub use db::Db;
 pub use query::Query;
 pub use query_result::QueryResult;
+pub use transaction::Transaction;

src/transaction.rs

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

tests/transaction_test.rs

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