Make npmbox work simultaneously

[arei]

If you run npmbox at the same time as another npmbox, the two will try to use the same directory (.npmbox-cache) which could cause conflicts. However, npmunbox requires that npmbox use this naming convention.

npmbox needs to use a temporary name structure when downloading the packages and then convert the name as it is being written into the .npmbox file so as to not create overlaps.

[danfuzz]

This is fixed in master and should be published soon (within a day or so).

[danfuzz]

Fixed in v4.2.0, just published.