Fix issue with watching (auto-regeneration) continuously running if destination is not '_site'. #457.

lib/jekyll/command.rb

@@ -1,9 +1,9 @@
 module Jekyll
   class Command
-    def self.globs(source)
+    def self.globs(source, destination)
       Dir.chdir(source) do
         dirs = Dir['*'].select { |x| File.directory?(x) }
-        dirs -= ['_site']
+        dirs -= [destination]
         dirs = dirs.map { |x| "#{x}/**/*" }
         dirs += ['*']
       end

lib/jekyll/commands/build.rb

@@ -56,7 +56,7 @@ module Jekyll
 
         dw = DirectoryWatcher.new(source)
         dw.interval = 1
-        dw.glob = self.globs(source)
+        dw.glob = self.globs(source, destination)
 
         dw.add_observer do |*args|
           t = Time.now.strftime("%Y-%m-%d %H:%M:%S")