Update README chat subcommand section

summary of diff --git  a/README.md b/README.md

- Update README.md to include a section on queries with chat history on local disk
- Explain how to execute more complex queries using the `chat` subcommand
- Describe the use of flags to provide a system message and specify local files as context
- Mention the ability to generate new files on local disk
- Provide an example command for generating a file in STORIES.md
- Add a section on automatically generating git commit messages with Grokker

README.md

@@ -80,18 +80,26 @@ subcommand is especially useful in editor sessions and when writing
 plugins -- more about this below. 
 ```
 
-You can execute more complex queries using the newer `chat`
+### Queries with chat history on local disk
+
+Execute more complex queries using the newer `chat`
 subcommand. This will create or append to an existing chat history
 file, and will use prior messages in the chat history as context.
-Flags allow you to provide a system message and one or more complete
-files as specific context or generate new files on local disk.  You
-can see an example of a generated file in [STORIES.md](./STORIES.md),
+Flags allow you to provide a system message.  You can specify local 
+files as context, and you can generate new files on local disk.  
+
+You can see an example of a generated file in [STORIES.md](./STORIES.md),
 which I created using the following command:
 
 ```
-echo "Write user stories for grokker based on the README." | grok chat STORIES.chat -s "You are a technical writer." -i README.md -o STORIES.md
+echo "Write user stories for grokker based on the README." \
+   | grok chat STORIES.chat \
+     -s "You are a technical writer." \
+     -i README.md -o STORIES.md
 ```
 
+### Automatically generating git commit messages
+
 Grokker can automatically generate git commit messages -- it will
 review the `git diff` of whatever you've staged, and generate a commit
 message on stdout.  See grokker's own commit history for examples of