Changed from sudo apt-get to the Travis apt addon for xmlsec1.

Author: Rebecka Gulliksson

.travis.yml

@@ -4,11 +4,13 @@ env:
   - TOX_ENV=py27
   - TOX_ENV=py34
 
+addons:
+  apt:
+    packages:
+    - xmlsec1
+
 services:
   - mongodb
 
-install:
-  - sudo apt-get install xmlsec1
-
 script:
   - ./setup.py test