Update to fix crypto text normalization.

This would update the readme for this exercise to be consistent with the source problem and to keep the idea of "square" more exact.  If this is changed, then the following change should be rejected:
https://github.com/exercism/xjavascript/pull/61

If this is rejected, that change should be accepted.
Merge pull request #28 from ClashTheBunny/patch-1

Update to fix crypto text normalization.