travis: install deps as suggested by travis manual (via before_install)

.travis.yml

@@ -2,12 +2,13 @@ language: cpp
 compiler:
   - gcc
   - clang
+before_install:
+ - sudo apt-get update -qq
+ - sudo apt-get install -qq python-pygments libqt4-core libqt4-gui libqt4-dev qt4-dev-tools qt4-qmake libxml2-utils
 script:
   - mkdir build
   - make test SRCDIR=build VERIFY=1 -j 4
   - ./cppcheck --error-exitcode=1 -Ilib --enable=style --suppress=duplicateBranch cli gui lib -igui/test
-  - sudo apt-get update
-  - sudo apt-get install python-pygments libqt4-core libqt4-gui libqt4-dev qt4-dev-tools qt4-qmake libxml2-utils
   - cd gui
   - qmake
   - make -j 4