Added documentation

Author: kmvanbrunt

CHANGELOG.md

@@ -9,6 +9,10 @@
     for formatting help/description text
     * Aliases are now sorted alphabetically
     * The **set** command now tab-completes settable parameter names
+    * Added ``async_alert``, ``async_update_prompt``, and ``set_window_title`` functions
+        * These allow you to provide feedback to the user in an asychronous fashion, meaning alert can be
+        display when the user is still entering text at the prompt. See [async_printing.py](https://github.com/python-cmd2/cmd2/blob/master/examples/async_printing.py)
+        for an example.
 * Deletions
     * The ``preparse``, ``postparsing_precmd``, and ``postparsing_postcmd`` methods *deprecated* in the previous release 
     have been deleted

README.md

@@ -40,6 +40,7 @@ Main Features
 - Trivial to provide built-in help for all commands
 - Built-in regression testing framework for your applications (transcript-based testing)
 - Transcripts for use with built-in regression can be automatically generated from `history -t`
+- Alerts that seamlessly print while user enters text at prompt
 
 Python 2.7 support is EOL
 -------------------------