Add simple benchmark

Cargo.toml

@@ -9,4 +9,9 @@ license = "Apache-2.0"
 err-derive = "0.2.4"
 
 [dev-dependencies]
+bencher = "0.1.5"
 once_cell = "1.4"
+
+[[bench]]
+name = "bench"
+harness = false

benches/bench.rs

@@ -0,0 +1,18 @@
+use std::path::PathBuf;
+
+use bencher::{benchmark_group, benchmark_main, Bencher};
+
+use word_segmenters::Segmenter;
+
+benchmark_group!(benches, short);
+benchmark_main!(benches);
+
+fn short(bench: &mut Bencher) {
+    let segmenter = Segmenter::from_dir(&PathBuf::from(format!(
+        "{}/data",
+        env!("CARGO_MANIFEST_DIR")
+    )))
+    .unwrap();
+
+    bench.iter(|| segmenter.segment("thisisatest"));
+}