Implement rudimentary control flow

demo/demo.rpy

@@ -1,13 +1,14 @@
-"Bob sat on the bench."
-"Bob" "Good morning!"
-    "Bob" "I am in a block now!"
-    "Bob" "Isn't this cool?"
-"Bob" "And now we're back in normal indentation."
-    "Bob" "We can even go multiple levels in!"
-        "Bob" "How far does the rabbit hole go?"
-        "Bob" "rabbit hole go?"
-        "Bob" "go?"
-"Bob" "Not sure what came of me there."
-"Bob" "I suppose I should eat a potato."
-eat "potato" True
-"Bob" "Yum!"
+# Control testing
+"Bob" "I will not say anything"
+if False:
+    "Bob" "W-what? Why am I saying this?"
+    if True:
+        "Testing 123"
+"..."
+"Bob" "Good."
+"Bob" "Now I will tell you my favorite food..."
+if True:
+    "Bob" "...cereal!"
+    if False:
+        "Bob" "But I actually hate it."
+"Bob sat on the bench."