Merge branch 'add_library_datetime' into 'master'

Agregate import to library datetime

Agregate datetime library, it has removed in commit previous

See merge request !108

l10n_mx_facturae_validate_cfdi/invoice.py

@@ -30,6 +30,7 @@ import xmltodict
 
 from suds.client import Client
 from xml.sax.saxutils import escape
+from datetime import datetime, timedelta
 
 from openerp.osv import orm
 from openerp.tools.translate import _