Fixed libmagickwand-dev library name

@devalih This should fix the #1 issue.
However, we might still need to run the command bellow on newly provisioned machines, if the update/provision doesn't install it.

```
$ cat /edx/app/edxapp/edx-platform/requirements/system/ubuntu/apt-packages.txt | xargs sudo apt-get install -yq
$ sudo su edxapp
$ pip install -r requirements/edx/edraak/certificates.txt
```