Remove the special config file

To execute Puppet for a NetApp device it is necessary to add an entry
to the device configuration file. This device configuration file holds
the certificate name of the device and the type of the device (in this
case netapp)

In the past you had to edit a second `netapp.yml` file where you can drop
the correct user credentials for your NetApp device. This does seem
redundant as the device configuration already specifies an url attribute
that can easily be used to store a username, a password and the hostname
of the device.

Use the URI instead and drop the special configuration file. This does
also make testing easier as you can overwrite the URI with a facts

Example

    FACTER_url=https://admin:secret@pfiler.example.com puppet resource netapp_user
Remove trailing whitespace in README.markdown
Update README to show a valid configuration example

After the special configuration file netapp.yml has been dropped, the
username and the password has to be included in the connection url.

Remove the part about the netapp.yml from the README and give a valid
example in how to specify an url
Remove obsolete tip in README.md

The netapp.yml is not necessary anymore as all connection attributes are
extracted from the configured url.
Fix typo in device.rb
Add vfiler support

NetApp allows multiple virtual filer to run on one physical filer. Every
API command runs under a specific vfiler context.

Managing a vfiler while connecting to the actual physical filer has the
benefit that you do not have to have network access to your vfiler
(e.g. you can place a vfiler in a DMZ network while your physical filer
is only accessable through your internal network).

The NetApp Server class already implements a method `set_vfiler` that
changes the context for all following api calls.

Allow passing a vfiler via the connection url. So instead of using

    [filer.example.com]
      type netapp
      url https://user:pw@filer.example.com

we accept the connection url `https://user:pw@filer.example.com/[virtalfiler]`
Merge pull request #45 from stschulte/feature/master/url_instead_file

Remove the special config file