Update .travis.yml

Build release package else win32 build gets useless debug Ogre dlls

.travis.yml

@@ -27,7 +27,7 @@ script:
 - cd build_qgears
 - cmake ..
 - make -j2
-- cpack -C Debug
+- cpack -C Release
 language: cpp
 after_success: 
 - hash=`git rev-parse HEAD`