upgrade jms serializer & update dependencies

composer.json

@@ -3,7 +3,8 @@
     "description": "a php lib for taskwarrior",
     "keywords": [
         "task",
-        "taskwarrior"
+        "taskwarrior",
+        "GTD"
     ],
     "type": "library",
     "license": "MIT",
@@ -15,16 +16,16 @@
     ],
     "require": {
         "php": ">=5.4",
-        "symfony/process": "~2.3",
-        "jms/serializer": "0.16.*",
-        "symfony/filesystem": "~2.3",
-        "nesbot/carbon": "~1.14",
-        "doctrine/collections": "~1.3",
+        "symfony/process": "^2.3",
+        "jms/serializer": "^1.0",
+        "symfony/filesystem": "^2.3",
+        "nesbot/carbon": "^1.14",
+        "doctrine/collections": "^1.3",
         "webmozart/path-util": "^2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.0",
-        "symfony/var-dumper": "~2.6"
+        "phpunit/phpunit": "^4.0",
+        "symfony/var-dumper": "^2.6"
     },
     "autoload": {
         "psr-4": {