Add alternative installation for kubectl and cfssl

Added alternative installation method for `kubectl` and `cfssl` via Homebrew

docs/02-client-tools.md

@@ -24,6 +24,12 @@ chmod +x cfssl cfssljson
 sudo mv cfssl cfssljson /usr/local/bin/
 ```
 
+Or install with Homebrew:
+
+```
+brew install cfssl
+```
+
 ### Linux
 
 ```
@@ -80,6 +86,12 @@ chmod +x kubectl
 sudo mv kubectl /usr/local/bin/
 ```
 
+Or install via Homebrew:
+
+```
+brew install kubectl
+```
+
 ### Linux
 
 ```