Fix pipeExpression order

This imitates Wonka's pipe algo so that it's easier
to follow. Also the previous one was incorrect

scripts/transform-pipe.js

@@ -1,14 +1,8 @@
 const pipeExpression = (t, pipeline) => {
-  if (pipeline.length === 1) {
-    return pipeline[0];
-  } else {
-    const operator = pipeline[pipeline.length - 1];
-    const rest = pipeline.slice(0, -1);
-    return t.callExpression(
-      pipeExpression(t, rest),
-      [operator]
-    );
-  }
+  let x = pipeline[0];
+  for (let i = 1; i < pipeline.length; i++)
+    x = t.callExpression(pipeline[i], [x]);
+  return x;
 };
 
 const pipePlugin = ({ types: t }) => ({