Update version from 0.6.1 to 0.7.2

From 0.6.1 to 0.7.2
This should be `target_file`

```
       Compiling Cookbooks...
       
       ================================================================================
       Recipe Compile Error in /tmp/kitchen/cookbooks/packer/recipes/default.rb
       ================================================================================
       
       NoMethodError
       -------------
       undefined method `target' for Chef::Resource::Link
       
       Cookbook Trace:
       ---------------
         /tmp/kitchen/cookbooks/packer/recipes/default.rb:29:in `block in from_file'
         /tmp/kitchen/cookbooks/packer/recipes/default.rb:22:in `from_file'
       
       Relevant File Content:
       ----------------------
       /tmp/kitchen/cookbooks/packer/recipes/default.rb:
       
        22:  link 'packer-to-packer-packer' do
        23:    # Unfortunately, upstream has stopped using a consistent naming scheme. This circumvents
        24:    # a strange case in which 0.7.1 does not contain 'packer', but 'packer-packer'.
        25:    link_type :symbolic
        26:    owner 'root'
        27:    group 'root'
        28:  
        29>>   target "/usr/local/packer-#{node[:packer][:version]}/packer"
        30:    to "/usr/local/packer-#{node[:packer][:version]}/packer-packer"
        31:  
        32:    not_if { ::File.exists?("/usr/local/packer-#{node[:packer][:version]}/packer") }
        33:  end
        34:  
       
       
       Running handlers:
       [2014-11-24T15:52:25+00:00] ERROR: Running exception handlers
       Running handlers complete
       [2014-11-24T15:52:25+00:00] ERROR: Exception handlers complete
       [2014-11-24T15:52:25+00:00] FATAL: Stacktrace dumped to /tmp/kitchen/cache/chef-stacktrace.out
       Chef Client failed. 0 resources updated in 6.294167737 seconds
       [2014-11-24T15:52:25+00:00] ERROR: undefined method `target' for Chef::Resource::Link
       [2014-11-24T15:52:25+00:00] FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)
```