docs: add quick intro to repl tool (#101)

docs: add quick intro to repl tool

README.md

@@ -12,9 +12,8 @@ Current commit on deltachat/deltachat-core: `12ef73c8e76185f9b78e844ea673025f56a
 ```sh
 # run example
 $ cargo run --example simple
-# build header file
+# build c-ffi
 $ cargo build -p deltachat_ffi --release
-$ cat deltachat-ffi/deltachat.h
 # run tests
 $ cargo test --all
 ```
@@ -23,3 +22,54 @@ $ cargo test --all
 [circle]: https://circleci.com/gh/deltachat/deltachat-core-rust/
 [appveyor-shield]: https://ci.appveyor.com/api/projects/status/lqpegel3ld4ipxj8/branch/master?style=flat-square
 [appveyor]: https://ci.appveyor.com/project/dignifiedquire/deltachat-core-rust/branch/master
+
+## Using the CLI client
+
+Run using `cargo`:
+
+```
+cargo run --example repl -- /path/to/db
+```
+
+Configure your account (if not already configured):
+
+```
+Delta Chat Core is awaiting your commands.
+> set addr your@email.org
+> set mail_pw yourpassword
+> configure
+```
+
+If you're already configured it's enough to `> connect`.
+
+Create a contact:
+
+```
+> addcontact yourfriends@email.org
+Command executed successfully.
+```
+
+List contacts:
+
+```
+> listcontacts
+Contact#10: <name unset> <yourfriends@email.org>
+Contact#1: Me √√ <your@email.org>
+```
+
+Create a chat with your friend and send a message:
+
+```
+> createchat 10
+Single#10 created successfully.
+> chat 10
+Single#10: yourfriends@email.org [yourfriends@email.org]
+> send hi
+Message sent.
+```
+
+For more commands type `> help`.
+
+```
+> help
+```