crypto/transposition - rail fence challenge modified

The cryptanalysis challenge "Transposition — rail fence" suffered from two main problems:
– key was badly chosen and the challenge was a corner case of the algorithm
– the cleartext was the result of an encryption instead of decryption as one would normally expect: this is against the philosophy behind this plateform, especially for easy challenges

The challenge has thus been rectified, previous validations were reset. Submitted solutions have also been removed as they were not correct but working for the corner case.

Thanks for your understanding!