core: remove use of virtualenv for Travis

.travis.yml

@@ -2,10 +2,9 @@ language: c
 
 before_install:
     - sudo apt-get update -qq
-    - sudo apt-get -y install devscripts equivs python-virtualenv virtualenvwrapper libenchant-dev
+    - sudo apt-get -y install devscripts equivs python-pip libenchant-dev
     - sudo mk-build-deps -i debian/control
-    - mkvirtualenv msgcheck
-    - pip install msgcheck
+    - sudo pip install msgcheck
 
 script:
     - mkdir build