Add underscores when querying column names

This commit aims to fix tests which fails on not finding columns such as
`expireson`. Adding the underscore that are used when creating the table
should fix this.

An issue with this is that it must have worked previously without underscores.
In that case this might break existing usage.

cleanup.go

@@ -53,6 +53,6 @@ func (db *PGStore) cleanup(interval time.Duration, quit <-chan struct{}, done ch
 
 // deleteExpired deletes expired sessions from the database.
 func (db *PGStore) deleteExpired() error {
-	_, err := db.DbMap.Exec("DELETE FROM http_sessions WHERE expireson < now()")
+	_, err := db.DbMap.Exec("DELETE FROM http_sessions WHERE expires_on < now()")
 	return err
 }