If you want to do some armchair Boston sight-seeing, make sure you’re following actor Treat Williams on Twitter. While in town to film the NBC pilot “Odyssey,” the actor has been tweeting photos of his stops at local historical sites. On Tuesday he took a picture of himself with a plaque dedicated to Declaration of Independence signer Robert Treat Paine. He captioned it, “Treat and Treat.”Mark Shanahan can be reached at firstname.lastname@example.org. Follow him on Twitter @MarkAShanahan. Meredith Goldstein can be reached at email@example.com. Follow her on Twitter @MeredithGoldste.