Customizable idle change delay
Document `flycheck-idle-change-delay`
Test `flycheck-idle-change-delay`
[Fix #144] Merge branch 'magnars-customizable-idle-change-delay'

* magnars-customizable-idle-change-delay:
  Test `flycheck-idle-change-delay`
  Document `flycheck-idle-change-delay`
  Customizable idle change delay
Fix RuboCop configuration file

The recent 0.8 release renamed some cops, so the configuration file
needs to be updated accordingly.