[fix] translation dev deps

requirements-dev.txt

+babel==2.2.0
 flake8==2.5.1
 mock==1.0.1
 nose2[coverage-plugin]
 plone.testing==4.0.15
 robotframework-selenium2library==1.7.4
 robotsuite==1.7.0
+transifex-client==0.11
 unittest2==1.1.0
 zope.testrunner==4.4.10