Assert output in some README examples

README.md

@@ -46,6 +46,9 @@ func main() {
 
 This app will run and show help text, but is not very useful. Let's give an action to execute and some help documentation:
 
+<!-- {
+  "output": "boom! I say!"
+} -->
 ``` go
 package main
 
@@ -77,6 +80,9 @@ Being a programmer can be a lonely job. Thankfully by the power of automation th
 
 Start by creating a directory named `greet`, and within it, add a file, `greet.go` with the following code in it:
 
+<!-- {
+  "output": "Hello friend!"
+} -->
 ``` go
 package main
 
@@ -210,6 +216,7 @@ Sometimes it's useful to specify a flag's value within the usage string itself.
 indicated with back quotes.
 
 For example this:
+
 ```go
 cli.StringFlag{
   Name:  "config, c",
@@ -504,6 +511,9 @@ templates are exposed as variables `AppHelpTemplate`, `CommandHelpTemplate`, and
 is possible by assigning a compatible func to the `cli.HelpPrinter` variable,
 e.g.:
 
+<!-- {
+  "output": "Ha HA.  I pwnd the help!!1"
+} -->
 ``` go
 package main