Use timeout function to force timeout on Travis. This will allow caching (#111)

.travis.yml

@@ -5,7 +5,6 @@ cache:
     - $HOME/.ccache
     - $HOME/.cache/pip
     - $HOME/docker
- #   - $TRAVIS_BUILD_DIR/external/
     - $TRAVIS_BUILD_DIR/external/Paddle/build/third_party
 
 sudo: required
@@ -24,26 +23,20 @@ addons:
       - python2.7-dev
   ssh_known_hosts: 13.229.163.131
 before_install:
-  -  sudo pip install pylint pytest astroid isort 
-  # Load cached docker images
-  #- if [[ -d $HOME/docker ]]; then ls $HOME/docker/*.tar.gz | xargs -I {file} sh -c "zcat {file} | docker load"; fi
+  - sudo pip install pylint pytest astroid isort 
+
+before_install:
+  - sudo pip install pylint pytest astroid isort
+  # Force the script to be timed out after certain duration
+  - function timeout() { perl -e 'alarm shift; exec @ARGV' "$@"; }
 
 jobs:
   include:
-    - script: scripts/deploy_docs.sh full 
+    # Force the deploy_docs.sh to time out after 40 minutes.
+    # Travis CI will terminate the build completely after 50 minutes and won't allow caching to happen.
+    # Time out the build preemptively to cache built libraries.
+    - script: timeout 2400 scripts/deploy_docs.sh full
       name: Generate Docs
-    - script: scripts/deploy_docs.sh pybind
-      name: Cache pybind build
-    - script: scripts/deploy_docs.sh proto
-      name: Cache proto build
-    - script: scripts/deploy_en_external_docs.sh
-      name: Generate EN external docs
-
-#before_cache:
-#  # Save tagged docker images
-#  - >
-#    mkdir -p $HOME/docker && docker images -a --filter='dangling=false' --format 'paddlepaddle/paddle:latest-dev {{.ID}}'
-#    | xargs -n 2 -t sh -c 'test -e $HOME/docker/$1.tar.gz || docker save $0 | gzip -2 > $HOME/docker/$1.tar.gz'
     
 notifications:
   email: