Add a better way to check if the current target is an specific OS

kickstart/recipes/kickstart.sh

@@ -3,6 +3,10 @@ kickstart.os() {
   ( uname -a | grep -q Darwin ) && echo "Mac"
 }
 
+kickstart.os.is() {
+  [[ `kickstart.os` == "$1" ]]
+}
+
 kickstart.codename() {
   lsb_release -sc
 }