* 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.
* Replaced assertJump, assertRevert and expectThrow with shouldFail.
* Fixed linter errors.
* Fixed typo.
* Made the helpers async.
(cherry picked from commit b0da0fded0)
* Extract standard token behaviuor to reuse it in other tests
* Add opt in ERC20 migration contract
* Make migration contract not to depend from standard token
* Changes based on feedback
* Improve MigratableERC20 inline documentation
* move behaviors to behaviors directory
* refactor MigratableERC20 into ERC20Migrator
* fix errors
* change expectEvent to support multiple events with same name
* fix tests
* update documentation
* rename MigratableERC20 files to ERC20Migrator
* move to drafts
* test beginMigration
* rename to ERC20Migrator
* missing semicolon (╯°□°）╯︵ ┻━┻
* add non-zero check
* improve documentation based on review comments
* improve test descriptions
* improve docs
* add getters
* fix contract
* improve tests
nikeshnazareth
Nicolás Venturo
Aniket
Facundo Spagnuolo