Fix load tester install command for zsh

docs/gitbook/usage/appmesh-progressive-delivery.md

@@ -38,7 +38,7 @@ Deploy the load testing service to generate traffic during the canary analysis:
 helm upgrade -i flagger-loadtester flagger/loadtester \
 --namespace=test \
 --set meshName=global.appmesh-system \
---set backends[0]=podinfo.test
+--set "backends[0]=podinfo.test"
 ```
 
 Create a canary custom resource:

docs/gitbook/usage/progressive-delivery.md

@@ -2,6 +2,8 @@
 
 This guide shows you how to use Istio and Flagger to automate canary deployments.
 
+### Bootstrap
+
 Create a test namespace with Istio sidecar injection enabled:
 
 ```bash
@@ -109,6 +111,8 @@ service/podinfo-primary
 virtualservice.networking.istio.io/podinfo
 ```
 
+### Automated canary promotion
+
 Trigger a canary deployment by updating the container image:
 
 ```bash
@@ -159,6 +163,8 @@ prod        frontend  Succeeded     0        2019-01-15T16:15:07Z
 prod        backend   Failed        0        2019-01-14T17:05:07Z
 ```
 
+### Automated rollback
+
 During the canary analysis you can generate HTTP 500 errors and high latency to test if Flagger pauses the rollout.
 
 Create a tester pod and exec into it: