Update README.

README.md

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 vibe.d core module
 ==================
 
+This is the designated successor of the `vibe-d:core` sub package of [vibe.d 0.7.x](https://github.com/rejectedsoftware/vibe.d.git). The API is mostly compatible from a library user point of view, but the whole library has received some heavy lifting under the surface, close to a rewrite. Most classes have been replaced by reference counting structs and `@safe nothrow` attributes are now used throughout the library, whenever possible. Adding `@nogc` still has to be decided, because of its viral nature.
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+Another major design change is that instead of the previous driver model, there is now a separate, lower-level event loop abstraction ([eventcore](https://github.com/vibe-d/eventcore.git)) which follows a callback based Proactor pattern. The logic to schedule fibers based on events has been pulled out of this abstraction and is now maintained as a single function, leaving to a huge improvment in terms of robustness (most issues in the previous implementation have probably never surfaced in practice, but there turned out to be lots of hidden bugs).
+
+The development state is still heavy work-in-progress.
 
 [![Build Status](https://travis-ci.org/vibe-d/vibe-core.svg?branch=master)](https://travis-ci.org/vibe-d/vibe-core)
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+
+Progress
+--------
+
+Feature             | State
+--------------------|---------
+Task scheduling     | done
+Concurrency         | done
+Streams             | WIP
+DNS lookup          | ---
+TCP connections     | done
+UDP connections     | ---
+File I/O            | ---
+Directory watchers  | ---
+ManualEvent         | unstable