Revert "RUBY-267 Cursor#alive?"

This reverts commit 05dfef2f11.
This adds new functionality and thus must wait for the 1.4 release.

lib/mongo/cursor.rb

@@ -307,13 +307,6 @@ module Mongo
     # @return [Boolean]
     def closed?; @closed; end
 
-    # Is this cursor alive on the server?
-    #
-    # @return [Boolean]
-    def alive?
-      @cursor_id && @cursor_id != 0
-    end
-
     # Returns an integer indicating which query options have been selected.
     #
     # @return [Integer]

test/cursor_test.rb

@@ -32,21 +32,6 @@ class CursorTest < Test::Unit::TestCase
     assert_kind_of Numeric, explaination['nscanned']
   end
 
-  def test_alive
-    batch = []
-    5000.times do |n|
-      batch << {:a => n}
-    end
-    @@coll.insert(batch)
-    cursor = @@coll.find
-    assert !cursor.alive?
-    cursor.next
-    assert cursor.alive?
-    cursor.close
-    assert !cursor.alive?
-    @@coll.remove
-  end
-
   def test_count
     @@coll.remove