Add pear modules, mail and net_smtp via composer (#93)

Add pear modules, mail and net_smtp via composer, remove php 5.6 build due to phpunit 6

.travis.yml

@@ -3,14 +3,13 @@ services:
 before_script:
   - echo "USE mysql;\nUPDATE user SET password=PASSWORD('dev') WHERE user='root';\nFLUSH PRIVILEGES;\n" | mysql -u root
 install:
-  - rm $TRAVIS_BUILD_DIR/tools/phpunit
-  - composer require --dev phpunit/phpunit ^5.7
-  - $TRAVIS_BUILD_DIR/vendor/bin/phpunit --version
-  - cp $TRAVIS_BUILD_DIR/vendor/bin/phpunit $TRAVIS_BUILD_DIR/tools
+  #- rm $TRAVIS_BUILD_DIR/tools/phpunit
+  #- composer require --dev phpunit/phpunit ~6.5.5
+  #- $TRAVIS_BUILD_DIR/vendor/bin/phpunit --version
+  #- cp $TRAVIS_BUILD_DIR/vendor/bin/phpunit $TRAVIS_BUILD_DIR/tools
 script: ant build-ci
 language: php
 php:
-  - '5.6'
   - '7.0'
   - '7.1'
 after_failure: "cat /tmp/icehrm.test.log"