To add the user bin folder to the path

Here thread https://github.com/jupyterhub/binderhub/issues/557

repo2docker/buildpacks/base.py

@@ -71,6 +71,9 @@ ENV {{item[0]}} {{item[1]}}
 {% endfor -%}
 {% endif -%}
 
+# So users can move executables here with postBuild, issue #557
+ENV PATH {{ /home/jovyan/{local}/bin:${PATH}}}
+
 {% if path -%}
 # Special case PATH
 ENV PATH {{ ':'.join(path) }}:${PATH}