Swap to PHP 7.0 and install ssh2 extension

Author: DivineOmega

.travis.yml

@@ -1,13 +1,9 @@
 language: php
 dist: xenial
-matrix:
-  include:
-    - php: '7.1'
-      before_install:
-        - sudo apt-get install software-properties-common
-        - sudo add-apt-repository ppa:ondrej/php -y
-        - sudo apt-get update
-        - sudo apt-get install -y php7.1-ssh2
+apt_packages:
+  - php-ssh2
+php:
+  - '7.0'
 install:
   - composer update
 script: