precedence on ~/texlive (won't use the system package texlive)

Author: yihui

.travis.yml

@@ -12,7 +12,7 @@ env:
 
 # capturing state, early exit if no integration test is needed
 before_install:
-  - export PATH=$PATH:$HOME/bin:$HOME/texlive/bin/x86_64-linux
+  - export PATH=$HOME/bin:$HOME/texlive/bin/x86_64-linux:$PATH
   - if [ ${TARGET} = integration ]; then
       if ! make integration-need; then
         echo "NOTE:"" Integration test skipped. To enable, create a branch named ${TRAVIS_BRANCH} in ${TRAVIS_REPO_SLUG}-examples.";