Cleanup box "Last-modified attribute" on "vagrant box remove"

[taurus-forever]

Hi!

First of all, thank you for useful plugin!

At the moment if I remove the box, then trying to fetch new one, plugin claims that updates have been found. Which is strange for me:

10:35:53 ✔ taurus:$ vagrant box remove XXXXX
Removing box 'XXXXX' with provider 'virtualbox'...
10:36:02 ✔ taurus:$ vagrant up XXXXX
Bringing machine 'XXXXX' up with 'virtualbox' provider...
[XXXXX] Verify remote image data: http://my.com/XXXXX.box
[XXXXX] Modified image detected : http://my.com/XXXXX.box {"Last-Modified"=>"Wed, 16 Oct 2013 05:51:04 GMT"}
Would you like to update the box? 
If negative - we keep ignoring this update, and notify only when another update detected. 
Type (Y/N)

IMHO, plugin just need to continue with downloading automatically if no local box found. So, IMHO, plugin should remove "Last-Modified" for the box on box removing stage.

Thank you!