Use user pk for user profile

Ghost User
2017-06-28T19:54:41+02:00

Closes #418

#### Previous behaviour
Steps to reproduce:

1. Open je account page
2. Open profiel
3. Niet jouw profiel (als de member pk niet de user pk is)

#### New behaviour
Steps to validate that it works:

1. Open je account page
2...

Closes #418 (closed)

Previous behaviour

Steps to reproduce:

1. Open je account page

2. Open profiel

3. Niet jouw profiel (als de member pk niet de user pk is)

New behaviour

Steps to validate that it works:

1. Open je account page

2. Open profiel

3. Wel jouw profiel (als de member pk niet de user pk is)