Add base branch logic

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

examples/hello.np

@@ -2,3 +2,27 @@ println(123);
 println(None);
 message = "hell world";
 println(message);
+
+if 1 {
+    println("OK");
+} else if 0 {
+    println("1 - fail?");
+} else {
+    println("2 - fail?");
+};
+
+if 0 {
+    println("3 - fail?");
+} else if 1 {
+    println("OK");
+} else {
+    println("4 - fail?");
+};
+
+if 0 {
+    println("5 - fail?");
+} else if 0 {
+    println("6 - fail?");
+} else {
+    println("OK");
+};