in Windows cmd.exe, testing for a file in a non-existant dir fails hard, so I rewrote the cfg dir code to keep trying until it finds an existant dir
if we're doing last resourt, use a directory that exists, not a .boot2docker subdir of it.
Revert "Revert "Merge pull request #70 from riobard/refactor/vbx""

This reverts commit 0c4effd44d8dd15b0c9a30d47cbd6d68b7183cbf.
Merge pull request #73 from SvenDowideit/test-for-cfg-dir-existance

Test for cfg dir existance
Use more efficient strings.NewReader
Merge pull request #75 from riobard/fix/revert

Revert "Revert "Merge pull request #70 from riobard/refactor/vbx""