Transform exercises in Stack projects

[rbasso]

Tracking migration of exercises to Stack projects

This issue is just for tracking. If you are interested in the discussion, please see #182.

Phase 1 - Preparing a proof-of-concept

• Change .gitignore to stop ignoring stack.yaml and packages.yaml.
• Change .travis.yml to support exercises that are already Stack projects.
• Migrate exercise pov to a Stack project.
• Add a stub solution to pov.

Phase 2 - Online-testing the proof-of-concept

• Check if fetching works as expected.
• Check if everything builds locally without problems.
• Check if submitting works as expected.

Phase 3 - Creating the transitional documentation

• Rewrite docs/INSTALLATION.md.
• Rewrite docs/TESTS.md.
• Rewrite README.md.
• Rewrite SETUP.md.

Phase 4 - Migrating all exercises

Part I

• pov
• lens-person
• forth
• zipper
• go-counting
• sgf-parsing
• parallel-letter-frequency
• connect
• simple-cipher
• sieve
• series
• secret-handshake
• say
• saddle-points
• pythagorean-triplet
• pig-latin
• pascals-triangle
• palindrome-products
• nth-prime

Part II

• custom-set
• linked-list
• food-chain
• wordy
• trinary
• octal
• ocr-numbers
• minesweeper
• house
• matrix
• clock
• luhn
• largest-series-product
• hexadecimal
• difference-of-squares
• binary-search-tree
• queen-attack
• robot-simulator
• kindergarten-garden
• crypto-square
• bank-account
• all-your-base
• atbash-cipher
• allergies
• raindrops
• prime-factors
• binary
• roman-numerals
• scrabble-score
• triangle

Part III

• beer-song
• meetup
• robot-name
• etl
• word-count
• list-ops
• simple-linked-list
• grade-school
• nucleotide-count
• phone-number
• anagram
• space-age
• rna-transcription
• hamming
• strain
• sum-of-multiples
• bob
• gigasecond
• grains
• sublist
• accumulate
• leap

Phase 5 - Creating the final documentation

• Rewrite docs/INSTALLATION.md.
• Rewrite docs/TESTS.md.
• Rewrite README.md.
• Rewrite SETUP.md.

Phase 6 - Cleaning up

• Rewrite .travis.yml.
• Remove _test and update config.json.
• Remove Vagrantfile.

Phase 7 - Updating the resolver

• Update .travis.yml to test match the latest working snapshot.
• Update exercises/*/stack.yaml to the same snapshot.