Compile warning removed, adding myself to contributors

CONTRIBUTORS

@@ -22,6 +22,7 @@
 #
 # Please keep the list sorted.
 
+Arne Beer <arne@twobeer.de>
 Christopher Seymour <chris.j.seymour@hotmail.com>
 David Coeurjolly <david.coeurjolly@liris.cnrs.fr>
 Dominic Hamon <dma@stripysock.com>

src/benchmark.cc

@@ -863,7 +863,7 @@ void Benchmark::RunInstance(const Instance& b, const BenchmarkReporter* br) {
 
 // Run the specified benchmark, measure its peak memory usage, and
 // return the peak memory usage.
-double Benchmark::MeasurePeakHeapMemory() {
+double Benchmark::MeasurePeakHeapMemory(const Instance&) {
   if (!get_memory_usage) return 0.0;
   double bytes = 0.0;
   /*  TODO(dominich)