mock modules that use exports.import path string

• supports mocking modules that use exports.import path string by using newest resolvewithplus,
• added live coverage badge to show, for example, 98% coverage,
• add linting for README examples,
• improve unit-test for mocking non-extensible objects and adding a comment,
• improve node-version definition of isLT1612 per review @aladdin-add,
• use smaller and specific condition for calling nextResolve at loader