Remove unnecessary and incorrect code regarding eslintrc
Remove unnecessary and incorrect code regarding eslintrc

This resolves the following issues:

* There's no need for the plugin to manually search for
  an .eslintrc config file in the current working directory.
  CLIEngine.executeOnText() "will assume that the text is a
  file in the current working directory, and so will still obey
  any .eslintrc and .eslintignore files that may be present."
  http://eslint.org/docs/developer-guide/nodejs-api#executeontext

* It's incorrect to set engineConfig.useEslintrc to an object,
  since useEslintrc must be a boolean:
  https://github.com/eslint/eslint/blob/v3.4.0/lib/cli-engine.js#L57

brunch/eslint-brunch,spyl94/eslint-brunch