improved pyd, README skeleton

+PyTeX: a LaTeX package to call Python from LaTeX
+================================================
+
+(C) 2017 Franck Pommereau <franck.pommereau@ibisc.univ-evry.fr>
+    GNU LGPL
+
+https://forge.ibisc.univ-evry.fr/fpom/pytex
+
+## Installation
+
+TODO
+
+## Usage
+
+TODO

@@ -81,6 +81,7 @@
   \py@write{#2}%
   \py@close
   \py@compile{eval}%
+  \expandafter\def\csname#1\endcsname{}%
   \pyx{makedef("#1", "\py@last")}%
 }
 

@@ -3,8 +3,6 @@
 \usepackage{pytex}
 \parindent=0pt
 
-\def\hello{NOT DEFINED}
-
 \begin{document}
 
 ***\pyv{" ".join(s.capitalize() for s in "hello world!".split())}***