fetch fails if files contain nested folders

[holandes22]

For example, when fetching
http://exercism.io/exercises/c/leap

we get the error ENOENT: no such file or directory, open '/home/pablo/exercism/c/leap/test/vendor/unity_internals.h'

So we need to create folders recursively.

This might break the logic in submit where the problem is obtained from the path as the format might vary