More URL niceness

• We’ve added an advanced option to give an individual post a custom URL.

• If you don’t want Tumblr automatically adding a summary to your permalink URLs, you can now disable the option “Use descriptive URLs” on your Customize page.

  (Disqus users:  Please do not adjust this setting just yet.)

• We’re also beginning to test an even nicer (!) URL format, inspired by the smart smart people at Vimeo.  We’re hoping to drop the “/post/” label, and simply link to “http://www.davidslog.com/1029”.  What do you think?   You can check it out on Marco’s tumblelog.