Use new way of defining services on packager.io

.pkgr.yml

 user: git
 group: git
+services:
+  - postgres
 before_precompile: ./bin/pkgr_before_precompile.sh
 targets:
   debian-7: &wheezy

bin/pkgr_before_precompile.sh

@@ -18,6 +18,3 @@ rm config/resque.yml
 
 # Set default unicorn.rb file
 echo "" > config/unicorn.rb
-
-# Required for assets precompilation
-sudo service postgresql start