Move hints from test suites and stub solutions to HINTS.md

[rbasso]

Currently we have some exercises with hints as comments in the test suite and/or in the stub solution.

Hints in the stub solutions are convenient - users are almost forced to read them - but proved to be a mess, because most users submit the code with the comments.

Hints in the test suite are not that bad, but they force the users to inspect it. I think that, ideally, users should get feedback running the tests, not studying them.

Anyway, considering that the contents of HINTS.md is automatically included in the README.md, it is the perfect place for hints. We just need to make it happen!

All the exercises that already have a HINTS.md file share the same formatting,

## Hints

so we are using this as a standard for now.

This issue will track the migration's progress as soon as we have a complete list of exercises to be changed.

Tracking changes

• allergies allergies: Move hints to HINTS.md #324
• bank-account bank-account: Move hints to HINTS.md #325
• binary-search-tree binary-search-tree: Move hints to HINTS.md #329
• clock clock: Move hints to HINTS.md #330
• custom-set custom-set: Move hints to HINTS.md #331
• forth forth: Move hints to HINTS.md #343
• go-counting go-counting: Move hints to HINTS.md #344
• grade-school grade-school: Move hints to HINTS.md #332
• lens-person hspec-lens-person: Rewrite test to use hspec with fail-fast. #381 (comments removed when ported to hspec)
• linked-list linked-list: Move hints to HINTS.md #333
• matrix matrix: Move hints to HINTS.md #334
• meetup meetup: Move hints to HINTS.md #335
• octal octal: Move hints to HINTS.md #383
• pov (nothing to fix)
• queen-attack queen-attack: Move hints to HINTS.md #336
• rna-transcription rna-transcription: Remove unneeded stub comments. #382 (comments removed)
• robot-name robot-name: Move hints to HINTS.md #337
• robot-simulator robot-simulator: Move hints to HINTS.md #338
• sgf-parsing sgf-parsing: Rewrite tests to use hspec with fail-fast. #300 (fixed when ported to hspec)
• simple-linked-list simple-linked-list: Move hints to HINTS.md #339
• space-age space-age: Move hints to HINTS.md #340
• sublist sublist: Move hints to HINTS.md #341
• trinary trinary: Move hints to HINTS.md #384
• wordy wordy: Move hints to HINTS.md #342
• zipper zipper: Rewrite tests to use hspec with fail-fast. #385 (comments removed when ported to hspec)

[rbasso]

Hints' migration to HINTS.md files finished. 😄