Buidler Beta 8

[alcuadrado]

This PR publishes Buidler Beta 8

The complete list of changes is:

• Buidler doesn't set a default evm version anymore (Let solidity choose the default evm version #277)
• Show stack traces on unknown errors ([core] Show stack traces on unknown errors #287)
• Config validation ([core] Config validation #285)
• Print a warning when ts-node fails to load (Print a warning when ts-node fails to load #289)
• Set the gasMultiplier to Truffle Contracts (Set the gas multiplier to Truffle Contracts #292)
• Fix multiple JSON-RPC errors (Set the gas multiplier to Truffle Contracts #292)
• Automatically Ganache gas estimations (Set the gas multiplier to Truffle Contracts #292)
• Change default gasMultiplier to 1 (Change default gasMultiplier to 1 #297)
• Make custom networks' url a required parameter (Make the network's url field a required parameter #298)
• Fix a bug that made buidler run and buidler console ignore some parameters (Forward Buidler arguments #300)