function mergeCLIPrereq(config) {
      if (opts.prereq) {
        config.prereq = (config.prereq || []).concat(opts.prereq.split(/\s*,\s*/));
      }
    }
Gathers all files that need to be linted, lints them, sends them to
a reporter and returns the overall result.

@param {object} post-processed options from 'interpret':
                args     - CLI arguments
                config   - Configuration object
                reporter - Reporter function
                ignores  - A list of files/dirs to ignore
                extensions - A list of non-dot-js extensions to check
@param {function} cb a callback to call when function is finished
                  asynchronously.

@returns {bool} 'true' if all files passed, 'false' otherwise and 'null'
                when function will be finished asynchronously.