Update documentation

- Fix an old link to the wrong issue tracker
- Add documentation to the history module about migration from oh-my-zsh

Closes #1766

modules/editor/README.md

@@ -106,4 +106,4 @@ Authors
 
   - [Sorin Ionescu](https://github.com/sorin-ionescu)
 
-[1]: https://github.com/sorin-ionescu/oh-my-zsh/issues
+[1]: https://github.com/sorin-ionescu/prezto/issues

modules/history/README.md

@@ -3,6 +3,10 @@ History
 
 Sets [history][1] options and defines history aliases.
 
+**Note:** If you are migrating from oh-my-zsh and want to keep your history, you
+will either need to set HISTFILE manually to `$HOME/.zsh_history` or rename
+`~/.zsh_history` to ~/.zhistory`.
+
 Options
 -------