Create host directory when using SyncFolders if it doesn't exist

[chooper]

Fixes #16

Includes error handling, such as:

$ bundle exec vagrant up --provider=aws
...
[default] Rsyncing folder: /tmp/docker/cant_write/ => ~/docker
There was an error when attempting to create a shared host folder.
Please inspect the error message below for more info.

Host path: /tmp/docker/cant_write/
Error: mkdir: cannot create directory `/tmp/docker': Permission denied

Also fixes a minor typo in the English locale for the rsync error message.

[mitchellh]

Unfortunately mkdir is not cross-platform safe. The biggest group of Vagrant users is on Windows. Instead, you should use FileUtils.mkdir_p and catch Errno::EPERM (I think, maybe EACCESS, I forget).

Otherwise, great patch. :)

[chooper]

Thanks for the comments! I'm swamped today but I think I can update the patch within the next 24-48 hours

[chooper]

Had some time on the train to update this :)

[titanous]

It's unlikely that you want to rescue Exception here. You probably want StandardError, as the former rescues exciting exceptions like SyntaxError and SignalException. This can be simplified to rescue => err.

[chooper]

Thanks for the advice @titanous. I've since updated this PR

[mitchellh]

This looks good. One more thing: The shared folder should only be created if the :created option is set. Otherwise, validation should actually pick up and error (Vagrant core handles).

See here: https://github.com/mitchellh/vagrant/blob/c1f53a4ace1a29309032952da3c9bc658314fda0/plugins/providers/virtualbox/action/share_folders.rb#L55

[tralamazza]

I've added the :create flag check, thanks for the PR