Update mount.rb

On Chef 11.16.4, line #19 fails with this error:

    NoMethodError: undefined method `device_name' for Chef::Resource::Mount

Removing the `private` access modifier makes the method call succeed.

Ruby 2.1.3p242
Ubuntu 12.04
Merge pull request #25 from rbrooks/patch-1

Update mount.rb
version bump; changelog update
version bump; changelog update; 1.1.2
Add additional flags attribute to pass to backup

This would satisfy the very few who need to override the temp and data
directories.
Adds addl_flags attribute to README
Merge pull request #26 from joraff/master

Add additional flags attribute to pass to backup
update changelog and version
Add support for passing mount options to the Mount resource.

Sometimes the cookbook implementer needs to pass comma-delimited options to the Mount command, for example, 'nfsvers=3'.