Remove obsolete development stages from README

Signed-off-by: Alex Coles <alex@alexbcoles.com>

README.md

@@ -11,45 +11,3 @@ You can use [aglio](https://github.com/danielgtaylor/aglio) to generate HTML doc
 ```bash
 aglio -i apiary.apib -o api.html
 ```
-
-Development stages
------------------------------
-
-The development of the OpenProject API v3 is split into multiple stages.
-This part of the document describes these stages, their's resources and
-endpoints.
-
-### Stage 1
-
-*Entry point:* `/`
-Providing basic API documentation and links to OpenProject API resources
-
-*Work packages:*
-* `PATCH /work_packages/:id`
-* `PATCH /work_packages?ids`
-* `GET /work_package`
-
-### Stage 2
-
-*Work packages:*
-* `GET /work_packages`
-* `POST /work_packages`
-* `DELETE /work_packages`
-
-*Projects:*
-* `GET /projects`
-* `GET /projects/:id`
-
-*Users:*
-* `GET /users/:id`
-
-*Versions:*
-* `GET /versions/:id`
-
-### Stage 3
-
-TODO
-
-### Stage 4
-
-TODO