Luhn: Update tests to 1.7.0 (1 changed tests, 2 new tests)

[tejasbubane]

Changes included:

1. Luhn: Update testcase to avoid wrong solution  problem-specifications#1480: 1.4.0 to 1.5.0:
   Change "055a 444 285" test into "055b 444 285" for subtle reasons.
   New test name: using ascii value for doubled non-digit isn't allowed

2. Luhn: Add a test with an odd number of spaces problem-specifications#1500: 1.5.0 to 1.6.0:
   Add test case: valid number with an odd number of spaces

3. luhn: check a number with an even remainder problem-specifications#1635: 1.6.0 to 1.7.0:
   Add test case: invalid long number with an even remainder

(Edit by @sshine: Added short description of the addressed commits.)

[sshine]

Thanks for your changes!

I found it difficult to decipher what test change was associated with what version change, since they're all in one commit. I didn't want to ask you to split them up before I knew how difficult that might be. A finer granularity comes at the cost of time spent now, but makes both reading git blame later and reviewing now much easier.

exercism/problem-specifictions#1480 renames changes a test, "valid strings with a non-digit included become invalid" into "using ascii value for non-doubled non-digit isn't allowed", even though it might look like one test was removed and another one was added.

The other two are simple test additions.

I'm approving this and will squash merge a short description of each canonical version bump to each mention in the PR and commit message so that future inspection is easier. Separate commits per version bump would also have worked.

[sshine]

I'm remarking that the comment above was left by 610ba69.

[tejasbubane]

A finer granularity comes at the cost of time spent now, but makes both reading git blame later and reviewing now much easier.

I'll be mindful of this in future. Thanks! 👍