update dependencies to minimum php 5.6 dependencies

composer.json

@@ -58,23 +58,23 @@
         "fix": "Fixes issues found by PHP-CS"
     },
     "require": {
-        "php": "^5.3.3 || ^7.0",
+        "php": "^5.6 || ^7.0",
         "ext-xml": "*",
         "zendframework/zend-escaper": "^2.2",
         "phpoffice/common": "^0.2.9"
     },
     "require-dev": {
         "ext-zip": "*",
         "ext-gd": "*",
-        "phpunit/phpunit": "^4.8.36 || ^7.0",
-        "squizlabs/php_codesniffer": "^2.9",
-        "friendsofphp/php-cs-fixer": "^2.2",
+        "phpunit/phpunit": "^5.7 || ^7.0",
+        "squizlabs/php_codesniffer": "^3.0",
+        "friendsofphp/php-cs-fixer": "^2.3",
         "phpmd/phpmd": "2.*",
-        "phploc/phploc": "2.* || 3.* || 4.*",
+        "phploc/phploc": "^4.0",
         "dompdf/dompdf":"0.8.*",
         "tecnickcom/tcpdf": "6.*",
-        "mpdf/mpdf": "5.7.4 || 6.* || 7.*",
-        "php-coveralls/php-coveralls": "1.1.0 || ^2.0"
+        "mpdf/mpdf": "7.*",
+        "php-coveralls/php-coveralls": "^2.0"
     },
     "suggest": {
         "ext-zip": "Allows writing OOXML and ODF",