scripts: add couchdb.check

from the README addition:


* `couchdb.check <COUCHDB URL>`
  Checks for active tasks on the CouchDB instance.  The info for the check will show the type and progress of each active task.
  e.g. `couchdb.check http://localhost:5984`
  * **Green:** No active tasks
  * **Pending/Green:** One or more active tasks. All tasks are at least 50% complete.
  * **Pending/Red:** One or more active tasks is less than 50% complete.