delegating the search logic to a query trait.

src/query/query.rs

@@ -0,0 +1,8 @@
+use std::io;
+use collector::Collector;
+use core::searcher::Searcher;
+use common::TimerTree;
+
+pub trait Query {
+    fn search<C: Collector>(&self, searcher: &Searcher, collector: &mut C) -> io::Result<TimerTree>;
+}