[FIX] transifex: actually escape strings containing a '

The report's template is wrong
should becomes

text:'The report\'s template is wrong'

but previous code had no effect

addons/transifex/models/ir_translation.py

@@ -86,6 +86,6 @@ class IrTranslation(models.Model):
                     'module': translation.module,
                     'src': werkzeug.url_quote_plus(
                             "text:'" +
-                            translation.source[:50].replace("'", "\'") +
+                            translation.source[:50].replace("'", "\\'") +
                             "'"),
                 }