switch composer to caret operator

Author: Jens Schulze

composer.json

@@ -23,23 +23,24 @@
     },
     "require": {
         "php": ">=5.4",
-        "psr/log": "~1.0",
-        "guzzlehttp/guzzle": "~5.0 | ~6.0",
-        "guzzlehttp/psr7": "~1.0",
-        "pimple/pimple": "~3.0"
+        "psr/log": "^1.0",
+        "guzzlehttp/guzzle": "^5.0 || ^6.0",
+        "guzzlehttp/psr7": "^1.0",
+        "pimple/pimple": "^3.0"
     },
     "require-dev": {
-        "guzzlehttp/guzzle": "~6.0",
-        "phpunit/phpunit": "~4.0",
-        "phpmd/phpmd": "~1.0",
-        "squizlabs/php_codesniffer": "~1.0",
-        "pdepend/pdepend": "~1.1",
-        "phploc/phploc": "~2.0",
-        "sebastian/phpcpd": "~1.4",
-        "mayflower/php-codebrowser": "~1.0",
-        "doctrine/cache": "~1.4",
-        "monolog/monolog": "~1.12",
-        "behat/behat": "~3.0",
+        "guzzlehttp/guzzle": "^6.0",
+        "phpunit/phpunit": "^4.0",
+        "phpmd/phpmd": "^1.0",
+        "squizlabs/php_codesniffer": "^1.0",
+        "pdepend/pdepend": "^1.1",
+        "phploc/phploc": "^2.0",
+        "sebastian/phpcpd": "^1.4",
+        "mayflower/php-codebrowser": "^1.0",
+        "doctrine/cache": "^1.4",
+        "monolog/monolog": "^1.12",
+        "behat/behat": "^3.0",
+        "phpspec/prophecy-phpunit": "^1.0",
         "phpunit/phpcov": "*"
     },
     "suggest": {