Fixed the composer constraints to have an upper bound

bin/skeleton/fat_composer.json

 {
     "require": {
-        "silex/silex": "dev-master",
+        "silex/silex": "1.0.*",
         "symfony/browser-kit": "2.1.*",
         "symfony/console": "2.1.*",
         "symfony/css-selector": "2.1.*",
@@ -16,8 +16,8 @@
         "symfony/validator": "2.1.*",
         "symfony/monolog-bridge": "2.1.*",
         "symfony/twig-bridge": "2.1.*",
-        "monolog/monolog": ">=1.0.0",
-        "twig/twig": ">=1.2.0",
+        "monolog/monolog": ">=1.0.0,<1.2-dev",
+        "twig/twig": ">=1.2.0,<2.0-dev",
         "doctrine/dbal": "2.1.*",
         "swiftmailer/swiftmailer": "4.1.*"
     }

bin/skeleton/slim_composer.json

 {
     "require": {
-        "silex/silex": "dev-master"
+        "silex/silex": "1.0.*"
     }
 }

composer.json

@@ -25,7 +25,7 @@
     "require-dev": {
         "symfony/security": "2.1.*",
         "symfony/form": "2.1.*",
-        "monolog/monolog": ">=1.0.0",
+        "monolog/monolog": ">=1.0.0,<1.2-dev",
         "symfony/browser-kit": "2.1.*",
         "symfony/css-selector": "2.1.*",
         "symfony/finder": "2.1.*",
@@ -34,7 +34,7 @@
         "symfony/translation": "2.1.*",
         "symfony/twig-bridge": "2.1.*",
         "symfony/validator": "2.1.*",
-        "twig/twig": ">=1.2.0",
+        "twig/twig": ">=1.2.0,<2.0-dev",
         "doctrine/dbal": "2.1.*",
         "swiftmailer/swiftmailer": "4.1.*"
     },