update travis config

* remove sudo
* cache pip
* setup DISPLAY for wkhtmltopdf
* use travis_after_tests_success

.travis.yml

@@ -1,8 +1,14 @@
+sudo: false
+cache: pip
+
 addons:
   apt:
-    packages:
+   sources:
+      - pov-wkhtmltopdf
+   packages:
       - expect-dev  # provides unbuffer utility
       - python-lxml # because pip installation is slow
+      - wkhtmltopdf
 
 language: python
 
@@ -17,11 +23,13 @@ env:
 virtualenv:
   system_site_packages: true
 
+before_install:
+  - "export DISPLAY=:99.0"
+  - "sh -e /etc/init.d/xvfb start"
+
 install:
   - git clone https://github.com/OCA/reporting-engine.git ${HOME}/reporting-engine -b ${VERSION}
   - git clone https://github.com/OCA/maintainer-quality-tools.git ${HOME}/maintainer-quality-tools
-  - wget http://download.gna.org/wkhtmltopdf/0.12/0.12.1/wkhtmltox-0.12.1_linux-precise-amd64.deb
-  - sudo dpkg -i wkhtmltox-0.12.1_linux-precise-amd64.deb
   - export PATH=${HOME}/maintainer-quality-tools/travis:${PATH}
   - travis_install_nightly
 
@@ -29,4 +37,4 @@ script:
   - travis_run_tests
 
 after_success:
-  coveralls
+  - travis_after_tests_success