[buildout] Checkout the beat.backend.python_v1.4.2_1 tag for beat.examples

This fixes the issue that the examples on the latest master are using
the 1.5 version of the python backend which is not yet released.

Relates to:
beat.examples#12

buildout.cfg

@@ -89,7 +89,7 @@ eggs = alabaster
 beat.core = git git@gitlab.idiap.ch:beat/beat.core
 beat.cmdline = git git@gitlab.idiap.ch:beat/beat.cmdline
 beat.backend.python = git git@gitlab.idiap.ch:beat/beat.backend.python
-beat.examples = git git@gitlab.idiap.ch:beat/beat.examples egg=false
+beat.examples = git git@gitlab.idiap.ch:beat/beat.examples egg=false rev=beat.backend.python_v1.4.2_1
 
 [scripts]
 recipe = bob.buildout:scripts