Document development status and start semantic versioning

Author: flowtoolz

README.md

@@ -1,13 +1,23 @@
 # SwiftNodes
 
-A Swift package providing a `Graph` data structure and various graph algorithms.
+👩🏻‍🚀 *This project [is still a tad experimental](#development-status). Contributors and pioneers welcome!*
 
-It serves as critical infrastructure for [Codeface.io](https://www.codeface.io).
+## What?
+
+SwiftNodes provides a `Graph` data structure and various graph algorithms.
+
+It serves as critical infrastructure for the [Codeface](https://www.codeface.io) app.
 
 ## Architecture
 
-Here is the internal composition with its essential dependencies:
+Here is the internal architecture (composition and essential dependencies):
 
 ![](Documentation/architecture.png)
 
-The above image was created with [Codeface.io](https://www.codeface.io).
+The above image was created with the [Codeface](https://www.codeface.io) app.
+
+## Development Status
+
+From version/tag 0.1.0 on, SwiftNodes adheres to [semantic versioning](https://semver.org). So until it has reached 1.0.0, its API may still break frequently, but this will be expressed in version bumps.
+
+SwiftNodes is already being used in production, but [Codeface](https://codeface.io) is still its primary client. SwiftNodes will move to version 1.0.0 as soon as its basic practicality and conceptual soundness have been validated by serving multiple real-world clients.