Update composer dependencies.

Bump supported version from PHP 5.5.9 to 5.6.0 (based on PHP LTS).

Author: tomzx

.travis.yml

@@ -1,7 +1,6 @@
 language: php
 
 php:
-    - 5.5
     - 5.6
     - 7.0
     - 7.1
@@ -12,7 +11,7 @@ sudo: false
 
 install:
     - composer self-update
-    - composer install --no-interaction --prefer-source
+    - composer install --no-interaction --prefer-dist
 
 script:
     - php vendor/bin/phpunit

composer.json

@@ -20,16 +20,16 @@
 		"issues": "https://github.com/tomzx/php-semver-checker/issues"
 	},
 	"require": {
-		"php": ">=5.5.9",
+		"php": ">=5.6.0",
 
-		"hassankhan/config": "^0.10",
+		"hassankhan/config": "^0.11",
 		"nikic/php-parser": "^3.1",
-		"symfony/console": "^2.7|^3.0",
-		"symfony/yaml": "^2.7|^3.0",
+		"symfony/console": "^2.7|^3.0|^4.0",
+		"symfony/yaml": "^2.7|^3.0|^4.0",
 		"tomzx/finder": "^0.1"
 	},
 	"require-dev": {
-		"mockery/mockery": "^0.9",
+		"mockery/mockery": "^1.0",
 		"phpunit/phpunit": "^4.0|^5.0"
 	},
 	"bin": [
@@ -47,7 +47,7 @@
 	},
 	"config": {
 		"platform": {
-			"php": "5.5.9"
+			"php": "5.6.0"
 		}
 	},
 	"extra": {