Expose the underlying connection from Rainbow Database so it's easier to use...

Expose the underlying connection from Rainbow Database so it's easier to use Dapper alongside other DB frameworks (#1257)

Dapper.Rainbow/Database.cs

@@ -175,6 +175,11 @@ public Table(Database<TDatabase> database, string likelyTableName)
         private int _commandTimeout;
         private DbTransaction _transaction;
 
+        /// <summary>
+        /// Get underlying database connection.
+        /// </summary>
+        public DbConnection Connection => _connection;
+
         /// <summary>
         /// Initializes the database.
         /// </summary>