fix lua index regen

.travis.yml

@@ -40,6 +40,7 @@ after_success:
           $TRAVIS_BRANCH == master -a \
           $TRAVIS_OS_NAME == linux -a \
           $TRAVIS_PULL_REQUEST == 'false' ]; then \
+         cd $TRAVIS_BUILD_DIR;
          git clone https://${GH_TOKEN}@github.com/Wargus/wargus.github.io;
          python3 -m pip install --user Pygments;
          python3 doc/lua/generate_index.py;