Lock versions for php 7.0

Signed-off-by: Julius Härtl <jus@bitgrid.net>

build/composer.json

@@ -1,6 +1,13 @@
 {
     "minimum-stability": "dev",
+    "repositories": [
+        {
+            "type": "vcs",
+            "url": "https://github.com/juliushaertl/reflection.git"
+        }
+    ],
     "require": {
-        "juliushaertl/phpdoc-to-rst": "dev-php7.0"
+        "juliushaertl/phpdoc-to-rst": "dev-php7.0",
+        "phpdocumentor/reflection": "dev-php7.0"
     }
 }