allow multiple local dependencies with the same directory name

[Dominic Burkart]

Currently turbolift only supports local dependencies with different directory names. /first/path and /second/path are considered invalid, since both paths end with (read: have a file_name of) /path, and a compile-time error is generated.

The error points to this issue so that I / others can see if this feature is important to implement. PRs for this fix are welcomed.