don't monkey-patch #default_provider

This monkey-patching of Vagrant::Environment#default_provider breaks
with Vagrant 1.7.0, since the method's signature changed.  In any case
Vagrant should do the right thing without "help" from vagrant-libvirt.
allow newer ruby-libvirt (#158)

As per #158, vagrant-libvirt depends on ruby-libvirt transitively
through fog.  Since fog/fog#2706 was resolved, fog now requires
ruby-libvirt ~> 0.5.0, therefore vagrant-libvirt should allow both 0.4.x
and 0.5.x.  Furthermore, according to semantic versioning, we currently
have no good reason to reject anything newer below 1.x.  If such a
restriction is required in the future (e.g. < 0.7.0) then it is likely
that fog's .gemspec will take care of that on our behalf anyway.

Closes #158.
allow cache mode to be set for additional disks
fix redirection of STDOUT/ERR of ssh port forwarding process (#226)

The existing invocation fails to spawn correctly, and even if that
were the case, redirecting STDOUT/STDERR to /dev/null risks losing
valuable debug, as seen in #225.

Closes #226.

https://github.com/pradels/vagrant-libvirt/issues/226
added ability to specify bus for additional disks
Merge pull request #261 from aspiers/remove-default-provider

don't monkey-patch #default_provider
Merge pull request #262 from aspiers/allow-newer-ruby-libvirt

allow newer ruby-libvirt (#158)
Merge pull request #263 from aspiers/extra-storage-cache-mode

allow cache mode to be set for additional disks
Merge remote-tracking branch 'upstream/master' into additional_disks_bus

Conflicts:
	README.md
	lib/vagrant-libvirt/config.rb
Merge pull request #270 from sciurus/additional_disks_bus

Additional disks bus
Merge pull request #264 from aspiers/ssh-forward-logging

fix redirection of STDOUT/ERR of ssh port forwarding process (#226)
Fix port forwarding ssh process cleanup

The presence of quotes in the command to spawn caused ruby to run it via
a shell instead of running it directly. This broke our code for
killing the ssh processes when the VM is halted.

Closes #265
Merge pull request #271 from sciurus/ssh-without-sh

Fix port forwarding ssh process cleanup
README.md : Fix `video_type` documentation.
Merge pull request #273 from crocket/master

README.md : Fix `video_type` documentation.
Merge pull request #1 from pradels/master

merging from upstream