Better English in failing_reasons

So that the status display and logs read more better.

Also, include the Zuul ref in JSON output so that the status
screen can do something intelligent with unprocessed items (also
it's an important bit of into).

Change-Id: I1429344917856edfaeefa4e9655c2dad8081cae5

zuul/model.py

@@ -304,6 +304,7 @@ class Pipeline(object):
             ret['item_ahead'] = None
         ret['items_behind'] = [i.change._id() for i in item.items_behind]
         ret['failing_reasons'] = item.current_build_set.failing_reasons
+        ret['zuul_ref'] = item.current_build_set.ref
         ret['project'] = changeish.project.name
         ret['enqueue_time'] = int(item.enqueue_time * 1000)
         ret['jobs'] = []

zuul/scheduler.py

@@ -998,7 +998,7 @@ class BasePipelineManager(object):
                 self.cancelJobs(item)
             self.prepareRef(item)
             if item.current_build_set.unable_to_merge:
-                failing_reasons.append("merge conflict")
+                failing_reasons.append("it has a merge conflict")
         if self.launchJobs(item):
             changed = True
         if self.pipeline.didAnyJobFail(item):
@@ -1007,7 +1007,7 @@ class BasePipelineManager(object):
             try:
                 self.reportItem(item)
             except MergeFailure:
-                failing_reasons.append("did not merge")
+                failing_reasons.append("it did not merge")
                 for item_behind in item.items_behind:
                     self.log.info("Resetting builds for change %s because the "
                                   "item ahead, %s, failed to merge" %