add benchmarks

benches/b15f.rs

@@ -0,0 +1,14 @@
+#![feature(test)]
+
+extern crate test;
+
+mod tests {
+	use super::*;
+	use test::Bencher;
+	use b15f::B15F;
+
+	#[bench]
+	fn bench_create_instance(b: &mut Bencher) {
+		b.iter(|| B15F::new());
+	}
+}