Implemented workaround for busybox issue.
Merge pull request #168 from diederikdehaas/workaround-for-busybox-static-v2

Implemented workaround for busybox issue.
Fixed the download URL for busybox-static.

Also implemented a proper check whether the download was succesful.
Merge pull request #169 from diederikdehaas/fix-busybox-download

Fixed the download URL for busybox-static.