Switch from Travis CI to GitLab CI

Using the very Ubuntu 14.04 (trusty) for now, because that's the closest
match to what Travis CI had at the time. Unfortunately, this build needs
a very particular combination of old package versions.

.gitlab-ci.yml

+build:
+  stage: build
+  image: ubuntu:trusty
+  variables:
+    DEBIAN_FRONTEND: noninteractive
+  before_script:
+    - sudo apt-get update
+    - sudo apt-get install -y dvipng python-imaging rubber texlive-fonts-recommended texlive-latex-extra texlive-math-extra
+    - wget -O plastex.tar.gz https://github.com/tiarno/plastex/archive/1.0.0.tar.gz
+    - tar -xzvf plastex.tar.gz
+    - cd plastex-1.0.0 && sudo python setup.py install
+  script:
+    - cd org.rodinp.handbook.feature
+    - ant -file customBuild.xml
+    - cd ..
+    - cp -r org.rodinp.handbook.feature/build/eclipse/* org.rodinp.handbook/
+    - mvn -f org.rodinp.handbook.parent/pom.xml install
+    - mkdir -p upload/current
+    - cp -r org.rodinp.handbook.feature/build/files upload/current/
+    - cp -r org.rodinp.handbook.feature/build/html upload/current/
+    - cp -r org.rodinp.handbook.feature/build/pdf upload/current/
+    - mkdir -p upload/updatesite
+    - cp -r org.rodinp.handbook.repository/target/repository/* upload/updatesite/
+    - cp org.rodinp.handbook.releng/index.html upload/updatesite/
+  artifacts:
+    paths:
+      - upload

.travis.yml

-sudo: required
-language: java
-before_install:
-  - sudo apt-get -qq update
-  - sudo apt-get install -y python-imaging rubber
-  - sudo apt-get install -y dvipng texlive-latex-extra texlive-math-extra texlive-fonts-recommended
-  - rvm install 2.0.0
-  - gem install travis-custom-deploy
-install:
-  - wget -O plastex.tar.gz https://github.com/tiarno/plastex/archive/1.0.0.tar.gz
-  - tar -xzvf plastex.tar.gz
-  - cd plastex-1.0.0 && sudo python setup.py install
-script:
-  - cd $TRAVIS_BUILD_DIR
-  - cd org.rodinp.handbook.feature
-  - ant -file customBuild.xml
-  - cd ..
-  - cp -r org.rodinp.handbook.feature/build/eclipse/* org.rodinp.handbook/
-  - mvn -f org.rodinp.handbook.parent/pom.xml install
-  - mkdir -p upload/current
-  - cp -r org.rodinp.handbook.feature/build/files upload/current/
-  - cp -r org.rodinp.handbook.feature/build/html upload/current/
-  - cp -r org.rodinp.handbook.feature/build/pdf upload/current/
-  - mkdir -p upload/updatesite
-  - cp -r org.rodinp.handbook.repository/target/repository/* upload/updatesite/
-  - cp org.rodinp.handbook.releng/index.html upload/updatesite/
-after_success:
-  - travis-custom-deploy sftp upload
-env:
-  global:
-  - secure: QfHLesV1wqgrSOLBAV8+7x977KxBcd5H6GIa+qxJZBDAKS7Dkp0yLdPtujBvC4CPPjcG6kZG89rDARRHU+XNC0C3w1ZzHjCuhYmd4eKOKwi0ENF9wBYi94Z5QVhDR37xq91lR09cnMh+ueBgu2XKiZJxAmbbcuo6lEEdeI0Arsc=
-  - secure: Cj47nbAhrPq+3x86d+TxHXnVC7GbS+ybnumNFeDmXww6c7+Ywsf+haYIgOuuoY2gFc6TAlbomvAdrBg+LVEYjIKblh7KJ+7QwSLCJPMHyuv41xTjqmp1KTHqDbInKsUUl5Hg+pHD1JzX3tSJ3SEqmTFiMpTjjE8SdtDpuIUDg+E=
-  - secure: cuoJ8L1wwA2NUCcSqnw1VcfnAkkudmcY3MByH6CSktPCDbcfwrjGfGZGzKQyl/2y5Ffjico9Htw/bO1xGNeII1H/iTLBv41jEupx8MNsfhBU2aSfsyViWox68ANljWyzp31F3Gmpwt3h+Xi/s/B+Mbq/QUjKfxsJeNgp2MdXgLU=
-  - secure: goK840fWiFfG6fIxj+YFx2yw2Le5MZwP3rlrKQKIvdY6+U9+rn9hzEIGqLpsUflr2KyqWkLc2iietrkYiLDlabObEwt/1FeISTxwit6J5nC7TH+oXFZGK18pj79EemdEdUQEVmFAVoh/ihykIbC5rR7ExP58CPE/BhSZPw432wY=
-notifications:
-  slack:
-    secure: IuoMqGlkcjXGX+HFmn+7Lb8XUisFID2CJOZcB5P1lAVH1I9l0hwBo4bYebe09FCk799FObCBG50Whet/swUnYN4ZQedkkAAR0h8UZB8HWLsfrJTBjIeIbaBzjZ75VkxAMMa9shodeV+jquupHZXyVul6aBmKzq7ydLy6lXYPx58=