Removing my precise64.box

I'm removing my box for two reasons:
1. It generate too much traffic for Dropbox, hence my public links are constantly disabled,
2. The box is quite old now, it no longer make any sense to use it.
I'll delete the box from my account soon, unless someone wants to host it. If you're interested, add a comment to that PR and I'll transfer it to you.
Thanks.
Merge pull request #324 from zyegfryed/patch-1

Removing my precise64.box