Add headings to README for clarity. (#337)

Author: paulosjca

README.md

@@ -16,23 +16,29 @@ gRPC OSS benchmarks are a collection of libraries and executables to schedule,
 run and monitor [gRPC performance benchmarking][benchmarking] tests on a
 Kubernetes cluster.
 
+### Controller
+
 The main executable is a [custom controller][] that manages resources of kind
 [LoadTest][loadtest]. This controller must be deployed to the cluster before
 load tests can be run on it. For deployment information, see [deployment][]. The
 controller is implemented with [kubebuilder][].
 
-There is also a set of [tools](tools/README.md) used to generate load test
+[custom controller]: cmd/controller/main.go
+[deployment]: doc/deployment.md
+[kubebuilder]: https://kubebuilder.io
+[loadtest]: config/crd/bases/e2etest.grpc.io_loadtests.yaml
+
+### Tools
+
+There is a set of [tools](tools/README.md) used to generate load test
 configurations, prepare prebuilt images and run batches of tests. These tools
 are used to run batches of tests for continuous integration.
 
+### Examples
+
 [Examples](config/samples/README.md) of load test configurations in the
 supported languages are also provided.
 
-[custom controller]: cmd/controller/main.go
-[deployment]: doc/deployment.md
-[kubebuilder]: https://kubebuilder.io
-[loadtest]: config/crd/bases/e2etest.grpc.io_loadtests.yaml
-
 ## Dashboard
 
 The data generated in continuous integration are saved to [BigQuery][bigquery],