Merge branch 'update-min-php7'

Closes #59

Author: akrabat

.travis.yml

@@ -3,9 +3,9 @@ sudo: false
 language: php
 
 php:
-  - 5.6
   - 7.0
   - 7.1
+  - 7.2
   - nightly
 
 matrix:

composer.json

@@ -23,12 +23,12 @@
     }
   ],
   "require": {
-    "php": ">=5.6",
+    "php": ">=7.0.0",
     "psr/http-message": "^1.0"
   },
   "require-dev": {
     "squizlabs/php_codesniffer": "^2.5",
-    "phpunit/phpunit": "^5.7|^6.0",
+    "phpunit/phpunit": "^6.0|^7.0",
     "php-http/psr7-integration-tests": "dev-master"
   },
   "provide": {