Vagrant wants older Virtualbox than is available in the repositories

[Aminda Suomalainen]

Vagrant wants Virtualbox 4.X, but the only one available in repositories is 5.0.

```
% vagrant up --provider=virtualbox
The provider 'virtualbox' that was requested to back the machine
'default' is reporting that it isn't usable on this system. The
reason is shown below:

Vagrant has detected that you have a version of VirtualBox installed
that is not supported. Please install one of the supported versions
listed below to use Vagrant:

4.0, 4.1, 4.2, 4.3
```

```
% LC_ALL=C apt-cache policy virtualbox
virtualbox:
  Installed: 5.0.0-dfsg-1
  Candidate: 5.0.0-dfsg-1
  Version table:
 *** 5.0.0-dfsg-1 0
        500 mirror://mirrors.ubuntu.com/mirrors.txt/ wily/multiverse amd64 Packages
        100 /var/lib/dpkg/status
```

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: vagrant 1.7.2+dfsg-4
ProcVersionSignature: Ubuntu 4.1.0-3.3-generic 4.1.3
Uname: Linux 4.1.0-3-generic x86_64
NonfreeKernelModules: fglrx
ApportVersion: 2.18-0ubuntu5
Architecture: amd64
CurrentDesktop:

Date: Thu Aug 6 10:09:31 2015
InstallationDate: Installed on 2015-07-31 (5 days ago)
InstallationMedia: Ubuntu-MATE 15.10 "Wily Werewolf" - Alpha amd64 (20150729)
PackageArchitecture: all
SourcePackage: vagrant
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Stepan Motin (smotin)]

The latest version of Vagrant (1.8.1) supports VirtualBox 5.X
Vagrant package upgrade to version >=1.8.1 would be appreciated.