Mocha Reporter Cov Summary完成所有测试后打印覆盖率摘要

mocha-reporter-cov-summary 完成所有测试后打印覆盖率摘要。用法在package.json ：\"scripts\": { \"test\": \"./node_modules/.bin/mocha --reporter node_modules/mocha-reporter-cov-summary test\" }将打印为：Coverage Summary: 1094 lines of 1253 lines, 87.3% covered