Keep duplicate github remotes from being added to component.json

My pull request #387 caused duplicate default github remotes to be added to the configuration each time the install command is ran. This was caused by moving the call to `saveConfig` after the addition of the default remote to `conf.remotes`. I also realized that the `forEach` loop is not needed in the code for pull req. #387 (issue #386) and refactored it accordingly.