Added command-line way to close issues.

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index e0bf935cd99cb2e74317f8dda2e89713e0b358af..e4c3a7154f00770b8b32b853a174597fd217b5df 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -1797,6 +1797,18 @@ def CMDset_commit(parser, args):
   return 0
 
 
+def CMDset_close(parser, args):
+  """close the issue"""
+  _, args = parser.parse_args(args)
+  if args:
+    parser.error('Unrecognized args: %s' % ' '.join(args))
+  cl = Changelist()
+  # Ensure there actually is an issue to close.
+  cl.GetDescription()
+  cl.CloseIssue()
+  return 0
+
+
 def Command(name):
   return getattr(sys.modules[__name__], 'CMD' + name, None)