be explicit about required dependencies

Depending on the FrameworkBundle implicitly pulling into all the
required packages is fragile and likely to break.

Author: xabbuh

.travis.yml

@@ -17,8 +17,6 @@ matrix:
   include:
     - php: 7.0
       env: COMPOSER_OPTIONS="--prefer-lowest --prefer-stable"
-    - php: 7.0
-      env: COMPOSER_OPTIONS=""
     - php: 7.1
       env: TEST_COVERAGE=true
   allow_failures:

composer.json

@@ -14,13 +14,17 @@
     "require": {
         "php": ">=5.3.3",
         "sentry/sentry": ">=1.5.0",
-        "symfony/framework-bundle": ">=2.4.0"
+        "symfony/config": "^2.4|^3.0",
+        "symfony/console": "^2.4|^3.0",
+        "symfony/dependency-injection": "^2.4|^3.0",
+        "symfony/event-dispatcher": "^2.4|^3.0",
+        "symfony/http-kernel": "^2.4|^3.0",
+        "symfony/security-core": "^2.4|^3.0"
     },
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^1.8.0",
         "phpunit/phpunit": "^4.6.6"
     },
-    "minimum-stability": "dev",
     "autoload": {
         "psr-0" : {
             "Sentry\\SentryBundle\\": "src/"