Output some error when require-dir tasks fails

It could be useful to see the results of the require tasks especially if there is an error.
Merge pull request #426 from alexanderchan/patch-1

Output some error when require-dir tasks fails
Fixes #441 - add custom logPrefix for BrowserSync
gulpfile - add `logPrefix` to the other browserSync instance

and single-quotes
Merge branch 'master' into GD

* master:
  gulpfile - add `logPrefix` to the other browserSync instance
  Fixes #441 - add custom logPrefix for BrowserSync
  Output some error when require-dir tasks fails