Removed php-5.6 environment from travis.yml

Removed php-5.6 environment from travis configuration since Magento 2.2 does not support it officially

Author: 4quaternion

.travis.yml

@@ -9,7 +9,6 @@ addons:
     - postfix
 language: php
 php:
-  - 5.6.29
   - 7.0
 env:
   global:
@@ -30,12 +29,6 @@ cache:
     - $HOME/.nvm
     - $HOME/node_modules
     - $HOME/yarn.lock
-matrix:
-  exclude:
-    - php: 5.6.29
-      env: TEST_SUITE=static
-    - php: 5.6.29
-      env: TEST_SUITE=js
 before_install: ./dev/travis/before_install.sh
 install: composer install --no-interaction --prefer-dist
 before_script: ./dev/travis/before_script.sh