Changelog

• Add Crowdsale contracts.
• Add a TokenTimelock contract.
• Add coveralls and move npm to yarn for TravisCI.
• Upgrade to Truffle version 3.2.2 and Solidity version 0.4.11
• Other minor refactors and fixes.
• Extract some functions of SafeMath into Math.
• Remove all checks for short address attack (see: #261)