* Add StandardBurnableToken implementation
BurnableToken that extends from StandardToken and adds a
burnFrom method that decrements allowance. Equivalent to
a transferFrom plus burn in a single operation.
* Return event object from expectEvent helper
* Add comment on Approval event in burnFrom function
* Improvements on burnable token tests
- Inject initial balance as a parameter to the behaviour
- Use expectEvent helper for assertions on events
- Use chai bignumber for numbers
- Change to bdd-style assertions
* Update to ganache-cli v6.1.0 and truffle v4.1.0
* Update to stable version of ganache-cli
* fix: update event emission warning
- Fix event emission warnings for solidity 4.21 after truffle has been
updated to use this version
* fix pr review comments
* update to truffle v4.1.5
* update package-lock
* add additional emit keywords
* update solidity-coverage to 0.4.15
* update to solium 1.1.6
* fix MerkleProof coverage analysis by testing through wrapper
* change version pragma to ^0.4.21
* fix solium linting errors
