Update README.md with link to things.http (#147)

Author: ehippy

README.md

@@ -147,6 +147,7 @@ The following open-source projects make use of this library:
 - [Things to OmniFocus via TaskPaper (wolf)](https://github.com/wolf/export-things-to-taskpaper)
 - [Things to Org file (chrizel)](https://github.com/chrizel/things-to-org)
 - [Things to Reclaim (cato447)](https://github.com/cato447/things2reclaim)
+- [Things.http (ehippy)](https://github.com/ehippy/things.http)
 - [CLI for Things](https://github.com/thingsapi/things-cli)
 - [GTD-like Reviews (minthemiddle)](https://github.com/minthemiddle/things-review-py)
 - [KanbanView for Things (AlexanderWillner)](https://github.com/AlexanderWillner/KanbanView)