Add bionic support

Author: zhengphou

.travis.yml

@@ -2,6 +2,27 @@ language: php
 
 matrix:
   include:
+    - dist: bionic
+      group: dev
+      env:
+        - RELEASE=bionic
+      name: xenial
+      php: '5.6'
+      before_install:
+        - sudo rm -rf /var/lib/apt/lists/lock /var/cache/apt/archives/lock /var/lib/dpkg/lock
+        - sudo apt-get update
+        - command -v expect || sudo apt-get install expect
+        - |
+          if ! command -v phpenv; then
+            pushd $HOME
+            curl -L http://git.io/phpenv-installer | bash
+            popd
+            export PHPENV_ROOT="/home/travis/.phpenv"
+            if [ -d "${PHPENV_ROOT}" ]; then
+              export PATH="${PHPENV_ROOT}/bin:${PATH}"
+              eval "$(phpenv init -)"
+            fi
+          fi
     - dist: xenial
       group: edge
       env: