Update readme-template.rst

use svg instead of png

templates/readme-template.rst

 .. vim: set fileencoding=utf-8 :
 .. <DATE>
 
-.. image:: http://img.shields.io/badge/docs-stable-yellow.png
+.. image:: http://img.shields.io/badge/docs-stable-yellow.svg
    :target: http://pythonhosted.org/<PACKAGE>/index.html
-.. image:: http://img.shields.io/badge/docs-latest-orange.png
+.. image:: http://img.shields.io/badge/docs-latest-orange.svg
    :target: https://www.idiap.ch/software/bob/docs/latest/bob/<PACKAGE>/master/index.html
 .. image:: https://gitlab.idiap.ch/bob/<PACKAGE>/badges/master/build.svg
    :target: https://gitlab.idiap.ch/bob/<PACKAGE>/commits/master
 .. image:: https://img.shields.io/badge/gitlab-project-0000c0.svg
    :target: https://gitlab.idiap.ch/bob/<PACKAGE>
-.. image:: http://img.shields.io/pypi/v/<PACKAGE>.png
+.. image:: http://img.shields.io/pypi/v/<PACKAGE>.svg
    :target: https://pypi.python.org/pypi/<PACKAGE>
-.. image:: http://img.shields.io/pypi/dm/<PACKAGE>.png
+.. image:: http://img.shields.io/pypi/dm/<PACKAGE>.svg
    :target: https://pypi.python.org/pypi/<PACKAGE>