update readme and revert the version for ep-extensions (#90)

README.md

@@ -48,13 +48,21 @@ In those branch:
 
     In this branch, Europa use substrate v3.0.0 from crate.io as dependencies, so as the `pallet-contracts` in vendor.
 
-* `substrate/v2.0.0` branch is fixed in v2.0.0 substrate and does not contains vendor:
+* `substrate/v2.0.0` branch is fixed in v2.0.0 substrate and does not contain vendor:
 
     > P.S. We do not advice you to use v2.0.0, for we no longer maintain this version.
 
 For master, Europa is tracking [newest substrate (deac6324)](https://github.com/paritytech/substrate/commit/deac6324a16fc4128b94a7b4c3826eebcb86917f) now. 
 Thus, `pallet-contracts` can use the newest features.
 
+> Note: The database format of Europa v0.3 and v0.2 is not compatible, please do not use the data generated by v0.2 as the data directory of v0.3 (`-d/--database parameter or use default data path`).
+> You should delete old database or use a new version.
+
+## Documentation
+[https://docs.patract.io/en/europa/introduction.html](https://docs.patract.io/en/europa/introduction.html)
+
+> Chinese: [https://docs.patract.io/europa/introduction.html](https://docs.patract.io/europa/introduction.html)
+
 ## Extending types
 When using [Substrate Portal](https://polkadot.js.org/apps), [@polkadot/api](https://github.com/polkadot-js/api) and [Redspot](https://github.com/patractlabs/redspot) or other 3rd parties clients to connect Europa `pallet-contracts` node, please remember to add ["extending types"](https://polkadot.js.org/docs/api/start/types.extend/) for Europa requirements.
 

primitives/extensions/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "ep-extensions"
-version = "0.3.2"
+version = "0.3.0"
 authors = ["patract labs <https://github.com/patractlabs>"]
 edition = "2018"