* ✏️ Refactor code & Refork OZ Repo

* Refactor ERC20Snapshot to use on-demand snapshots.

* Add ERC20Snapshot changelog entry.

* Move ERC20Snapshot to drafts.

* Improve changelog entry.

* Make snapshot tests clearer.

* Refactor ERC20Snapshots to use Counters.

* Refactor snapshot arrays into a struct.

* Remove .DS_Store files.

* Delete yarn.lock

* Fix linter error.

* simplify gitignore entry

* Add _setTokenURI internal.

* Rename TokenMetadata to ERC20Metadata.

* Add changelog entry for ERC20Metadata.

* Fix linter error.

* Add breaking change changelog notice.

* Updated code style to no more than120 characters per line.

* Unify code comments style with Doxygen-style tags.

* Add back solidity-coverage (using fork).

* Pin fork version.

* Improve SafeMath test coverage.

* Fix linter error.

* Split testCommutative into something more sane.

* Refactor Counter to support increment and decrement.

* Move Counter out of drafts.

* Refactor ERC721 to use Counter.

* Rollback Counter returning the current value in increment and decrement.

* Update test/drafts/Counter.test.js

Co-Authored-By: nventuro <nicolas.venturo@gmail.com>

* Improve Counter documentation.

* Move Counter.test to utils.

* Move back Counter to drafts.

* Add ERC20._approve.

* Add ERC20._approve tests.

* Fix linter error.

* Require owner in _approve to be non-zero.

* Bump required compiler version to 0.5.2.

* Fix shadowed variable warning in ERC20Migrator.

* Rename Counter to Counters.

* Add dummy state variable to SafeERC20Helper.

* Update changelog entry.

* Fix CountersImpl name.

* Improve changelog entry.

* Now compiling using truffle 5.

* Migrated some test files, missing BN scientific notation usage.

* Now using BN time values.

* Migrate ERC20 tests.

* Migrate all ERC20 tests.

* Migrate utils, payment and ownership tests.

* All tests save ERC721 migrated.

* Migrated ERC721 tests.

* Fix lint errors.

* Delete old test helpers.

* Fix remaining crowdsale tests.

* Fix signature bouncer tests.

* Update how constants is used.

* Compile script pre-removes the build dir.

* Fix SafeMath tests.

* Revert "Compile script pre-removes the build dir."

This reverts commit 247e7451135d33c056a126e9e5fd77a24348018d.

* Fix linter errors.

* Upgrade openzeppelin-test-helpers dependency.

* Update openzeppelin-test-helpers dependency.

* Define math constants globally.

* Remove unnecessary ether unit.

* Roll back reduced ether amounts in tests.

* Remove unnecessary toNumber conversions.

* Delete compile script.

* Fixed failing test.

* Adding solhint, working on style fixes.

* Upgraded to solhint 1.5.0.

* Removed all references to Solium

* Updated mocks to make the pass the new linter rules.

* Reformatted the .solhint.json file a bit.

* Removed Solium configuration files.

* Remove Solium dependency.

* Add comment explaing disabled time rule in TokenVesting.

* Revert to the old (ugly?) style.

* Revert SignatureBouncerMock style.

* Fix ERC165InterfacesSupported interface.

* Rename WhitelisterRole to WhitelistAdminRole.

* Update WhitelistAdmin changelog entry.

* separate unsigned and signed safemath libraries

* update changelog entry for SignedSafeMath

* signing prefix added

* Minor improvement

* Successfully tested

* Minor improvements

* Minor improvements

* Revert "Dangling commas are now required. (#1359)"

This reverts commit a6889776.

* updates

* fixes #1404

* approve failing test

* suggested changes done

* ISafeERC20 removed

* conflict fixes

* added examples

* fixes #706

* linting

* fixes #204

* file fixing

* deep bignumber comparison removed

* Update SafeERC20Helper.sol

* Update IERC20.sol

* Update SafeERC20.sol

* Update package-lock.json

* Revert "deep bignumber comparison removed"

This reverts commit 230b27214fc96ab4c990b169bbc15df129bad657.

(cherry picked from commit 73cbad2f)

(cherry picked from commit 50367416)