fixing import for SafeERC20 and IERC20;
set up constructor for synthetix connector to set address for staking contract;
created MockSynthetix.sol for test;
added nomiclabs/buidler;
fixed test for SynthetixProtocol.js;
adding .gitatributes to highlight solidity on GitHub;
adding buidler artefacts and cache to git ignore;
adding buidler.config.js;
adding connectorID method in connector as override and set model, id in constructor;
modify migration to deploy and set model, id;
update ganache to unlock master;
fixing curveProtocol test to use master address and get dai from uniswap;
fixing curveSBTCProtocol test to use cast for the sell connector method;
