minor #1181 Remove usage of the deprecated target-dir feature (stof)

This PR was squashed before being merged into the 2.0.x-dev branch (closes #1181).

Discussion
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Remove usage of the deprecated target-dir feature

Commits
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641c60cb Remove usage of the deprecated target-dir feature

src/Silex/Api/composer.json

@@ -24,9 +24,8 @@
         "silex/silex": "For BootableProviderInterface and ControllerProviderInterface"
     },
     "autoload": {
-        "psr-0": { "Silex\\Api": "" }
+        "psr-4": { "Silex\\Api\\": "" }
     },
-    "target-dir": "Silex/Api",
     "extra": {
         "branch-alias": {
             "dev-master": "2.0.x-dev"

src/Silex/Provider/composer.json

@@ -21,9 +21,8 @@
         "silex/api": "~2.0"
     },
     "autoload": {
-        "psr-0": { "Silex\\Provider": "" }
+        "psr-4": { "Silex\\Provider\\": "" }
     },
-    "target-dir": "Silex/Provider",
     "extra": {
         "branch-alias": {
             "dev-master": "2.0.x-dev"