Backports PR #8981
**Commit 1:**
Add checkPlugins task to check for plugins before running tests.
* Original sha: 9e71c779ba
* Authored by CJ Cenizal <cj@cenizal.com> on 2016-11-05T05:02:13Z
**Commit 2:**
Remove checkPlugins npm script. Gracefully handle error case.
* Original sha: 98ec182915
* Authored by CJ Cenizal <cj@cenizal.com> on 2016-11-09T20:51:47Z
**Commit 3:**
Move checkPlugins task into its own module.
* Original sha: bba727461d
* Authored by CJ Cenizal <cj@cenizal.com> on 2016-11-15T23:40:41Z
