Add an example

Author: jedisct1

README.md

@@ -4,4 +4,24 @@ Precision is a simple crate to perform measurements using hardware counters.
 
 It is especially useful for performing micro-benchmarks.
 
-[API documentation](https://docs.rs/precision)
+## [API documentation](https://docs.rs/precision)
+
+## Example
+
+```rust
+extern crate precision;
+
+let p = precision::Precision::new(precision::Config::default()).unwrap();
+
+let start = p.now();
+let stop = p.now();
+let elapsed1 = stop - start;
+
+let start = p.now();
+let stop = p.now();
+let elapsed2 = stop - start;
+
+let elapsed_total = elapsed1 + elapsed2;
+let elapsed_total_secs = elapsed_total_as_secs_f64();
+let hw_ticks = elapsed_total.ticks();
+```