* removed unnecessary require

* build pipeline fix

* kept as it is

* Added require

* removing unused variables

* undeleting the _

* replacing all instances of from: anyone with from: other

* replacing all instances of from: anyone with from: other

* replacing all instances of from: anyone with from: other

* changing anyone to other

* changing anyone to other

* Update PaymentSplitter.sol

* add back private function docs

* add non-zero address requirement

* add comprehensive contract-level docs

* use capital E for Ether

This reverts commit 07fc8c73.

* Remove unused dependencies.

* Remove unused mock contracts.

* Added basic punctuation to @dev docs (#1697)

* add missing uppercase

Added Buidler.

* Add barebones EIP1820 support.

* Update openzeppelin-test-helpers dependency to have ERC1820 support.

* Add tests for ERC1820.

* Improve inline documentation.

* Add changelog entry.

* Update test-helpers, refactor tests to use new helpers.

* Rename ERC1820 to ERC1820Implementer.

* Improve implementer docstring.

* Remove _implementsInterfaceForAddress.

* update openzeppelin-test-helpers to 0.2.0

* Update contracts/drafts/ERC1820Implementer.sol

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

* Fix how solidity coverage is run to allow for free events.

* Fix coverage testing script.

* Add API stability doc link.

* Update README.md

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

* Replace mentions of Slack for forum links.

* make forum lowercase

* Rename variable from thing to contractUnderTest

* Compute function signatures in ERC165 interfaces

The ERC165 tests currently precompute some known interface ids.
This commit extracts the interfaces into a separate object and
precomputes the individual function signatures.

This will be useful to identify contracts that support an interface
but do not implement all of the corresponding functions.

* Add tests for ERC165 interface implementations

The ERC165 tests confirm that contracts claim to support
particular interfaces ( using the supportsInterface method )

This commit extends those tests to confirm that the corresponding
functions are included in the contract ABI.

It also rewords the existing test names in order to group the
implementation tests with the corresponding interface tests.

* Remove obsolete ERC721Exists interface constant

* Transaction Malleability:
If you allow for both values 0/1 and 27/28, you allow two different
signatures both resulting in a same valid recovery. (r,s,0/1) and
(r,s,27/28) would both be valid, recover the same public key and sign
the same data. Furthermore, given (r,s,0/1), (r,s,27/28) can be
constructed by anyone.

* Transaction Malleability:
EIP-2 still allows signature malleabality for ecrecover(), remove this
possibility and force the signature to be unique.

* Added a reference to appendix F to the yellow paper and improved
comment.

* better test description for testing the version 0, which returns
a zero address

* Check that the conversion from 0/1 to 27/28 only happens if its 0/1

* improved formatting

* Refactor ECDSA code a bit.

* Refactor ECDSA tests a bit.

* Add changelog entry.

* Add high-s check test.

* Add extcodesize check to SafeERC20.

* Clarify some comments.

* Replace inline assembly with Address.sol.

* Add TimedCrowdsale::_extendTime

* Add tests for TimedCrowdsale extending method

* Reverse event arguments order

* Rename method argument

* Refactor TimedCrowdsale test

* Simplify TimedCrowdsaleImpl

* Fix extendTime method behaviour to deny TimedCrowdsale re-opening after it was ended

* Append chengelog

* Update CHANGELOG.md

Co-Authored-By: k06a <k06aaa@gmail.com>

* Update contracts/crowdsale/validation/TimedCrowdsale.sol

Co-Authored-By: k06a <k06aaa@gmail.com>

* Improve tests

* Add guard to ERC20Migrator migrate function

* Add tests for premature migration in ERC20Migrator

These tests apply to the new guard condition, but they don't
fail without it, since the functions revert anyway.
They are added for completeness and to ensure full code coverage.

* Use context block around premature migration tests

We should use context blocks for situational details
and describe for features or functions.

* rename previous audit to date it was performed

* add latest audit

* add note about latest audit in README

Using "a" instead of "an" makes this consistent with the comment on `allowance`.

* Add no-return-data ERC20 support to SafeERC20.

* Add changelog entry.

* Replace abi.encodeWithSignature for encodeWithSelector.

* Remove SafeERC20 test code duplication.

* Replace assembly for abi.decode.

* Fix linter errors.