Increased latest version to 2.1.9b0 [skip ci]

README.rst

 .. vim: set fileencoding=utf-8 :
 .. Tue 27 Feb 2018 09:06:28 CET
 
-.. image:: https://img.shields.io/badge/docs-v2.1.8-yellow.svg
-   :target: https://www.idiap.ch/software/bob/docs/bob/bob.buildout/v2.1.8/index.html
+.. image:: https://img.shields.io/badge/docs-stable-yellow.svg
+   :target: https://www.idiap.ch/software/bob/docs/bob/bob.buildout/stable/index.html
 .. image:: https://img.shields.io/badge/docs-latest-orange.svg
    :target: https://www.idiap.ch/software/bob/docs/bob/bob.buildout/master/index.html
-.. image:: https://gitlab.idiap.ch/bob/bob.buildout/badges/v2.1.8/build.svg
-   :target: https://gitlab.idiap.ch/bob/bob.buildout/commits/v2.1.8
-.. image:: https://gitlab.idiap.ch/bob/bob.buildout/badges/v2.1.8/coverage.svg
-   :target: https://gitlab.idiap.ch/bob/bob.buildout/commits/v2.1.8
+.. image:: https://gitlab.idiap.ch/bob/bob.buildout/badges/master/build.svg
+   :target: https://gitlab.idiap.ch/bob/bob.buildout/commits/master
+.. image:: https://gitlab.idiap.ch/bob/bob.buildout/badges/master/coverage.svg
+   :target: https://gitlab.idiap.ch/bob/bob.buildout/commits/master
 .. image:: https://img.shields.io/badge/gitlab-project-0000c0.svg
    :target: https://gitlab.idiap.ch/bob/bob.buildout
 .. image:: https://img.shields.io/pypi/v/bob.buildout.svg

version.txt

-2.1.8
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+2.1.9b0
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