Address could not change directory to "/home/vagrant": Permission denied

* Without this change:
```
default: installing PostgreSQL
default: could not change directory to "/home/vagrant": Permission denied
default: could not change directory to "/home/vagrant": Permission denied
default: could not change directory to "/home/vagrant": Permission denied
default: installing MySQL
```

* With this change:
```
default: installing PostgreSQL
default: installing MySQL
```

Author: yahonda

bootstrap.sh

@@ -36,9 +36,9 @@ install Redis redis-server
 install RabbitMQ rabbitmq-server
 
 install PostgreSQL postgresql postgresql-contrib libpq-dev
-sudo -u postgres createuser --superuser vagrant
-sudo -u postgres createdb -O vagrant -E UTF8 -T template0 activerecord_unittest
-sudo -u postgres createdb -O vagrant -E UTF8 -T template0 activerecord_unittest2
+sudo -i -u postgres createuser --superuser vagrant
+sudo -i -u postgres createdb -O vagrant -E UTF8 -T template0 activerecord_unittest
+sudo -i -u postgres createdb -O vagrant -E UTF8 -T template0 activerecord_unittest2
 
 debconf-set-selections <<< 'mysql-server mysql-server/root_password password root'
 debconf-set-selections <<< 'mysql-server mysql-server/root_password_again password root'