* 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.