bump to 7.1

Author: ashnazg

composer.json

@@ -19,7 +19,7 @@
         }
     },
     "require": {
-        "php": "^7.0",
+        "php": ">=7.1",
         "psr/log": "~1.0",
         "nikic/php-parser": "^3.0",
         "phpdocumentor/reflection-docblock": "^4.1",
@@ -29,7 +29,8 @@
         "mockery/mockery": "~1.0",
         "mikey179/vfsStream": "~1.2",
         "squizlabs/php_codesniffer": "^2.5",
-        "phpunit/phpunit": "^6.4"
+        "phpunit/phpunit": "~6.5",
+        "phpstan/phpstan": "^0.9.0"
     },
     "extra": {
         "branch-alias": {