try to build epub, mobi and pdf on Travis CI

refer https://github.com/athena-oss/athena/blob/master/.travis.yml

.travis.yml

@@ -1,15 +1,33 @@
 language: java
 jdk:
   - oraclejdk8
-install:
+sudo: required
+before_install:
   - nvm install
-  - nvm use
+  - npm install -g svgexport
+  # https://calibre-ebook.com/download_linux
+  - sudo -v && wget -nv -O- https://download.calibre-ebook.com/linux-installer.sh | sudo sh /dev/stdin
+  - sudo ln -s /opt/calibre/ebook-convert /usr/local/bin/
+install:
   - npm install
   - ./mvnw install -DskipTests=true -B
 script:
   - npm test
   - ./mvnw verify -B
-sudo: false
+  - travis_wait npm run epub
+  - travis_wait npm run mobi
+  - travis_wait npm run pdf
 cache:
   directories:
     - node_modules
+deploy:
+  provider: releases
+  api_key:
+    secure: "T72dusk4McXA72qrJmSBVEkTzT7B/jKXujl39TcwjEWRlgmodldRBg0W/3n3L2thl2d72mIXaHYTmYUa1GT3Stvg4oZamYZD3/AVbDeGL7DKLixc/dfIK5ib8Hu4lZLRx0iP/BC5F9laj1GlzIGwkp7RwqltvPmB0DTcFVRhMco="
+  file:
+    - 'what-is-maven.epub'
+    - 'what-is-maven.mobi'
+    - 'what-is-maven.pdf'
+  skip_cleanup: true
+  on:
+    tags: true

package.json

@@ -13,6 +13,8 @@
   "scripts": {
     "postinstall": "gitbook install",
     "test": "gitbook build",
+    "epub": "gitbook epub ./ ./what-is-maven.epub",
+    "mobi": "gitbook mobi ./ ./what-is-maven.mobi",
     "pdf": "gitbook pdf ./ ./what-is-maven.pdf",
     "pretest": "textlint '!(node_modules)/*.md'"
   },