upload!() should honor within()

[docwhat]

The upload!() (and download()) methods should both honor within() for relative paths.

Example:

within '/tmp/' do
  upload! '/etc/hosts', 'should-be-in-tmp'
end

I expect the file should-be-in-tmp to be in /tmp/ but instead it is in the user's home directory.

Ciao!

[leehambley]

We'll be glad of a pull request, otherwise I can't imagine that I'll ever have time to implement this.

[mikz]

Duplicate of #329 which is more active.

[leehambley]

Thanks for the GC hint @docwhat