i18n: add update script

Tuleap: #18
Change-Id: Id5ca78ba6e4c47f06c8c3efc5a869769e38f9f76

README.md

@@ -38,6 +38,11 @@ git clean -dfx
 
 And start again
 
+## Update translations
+
+Update translations using the Transifex client (tx) :
+./update-translations.sh
+
 ## Common issues
 
 * Makeinfo issue

update-translations.sh

+#!/bin/bash
+tx pull -af --minimum-perc=75