Removes verbiage about unsuitability for async apps

It's not entirely true, particularly if you build the runner and
emitters at runtime. An emitter could potentially write to an async
promise and/or I/O stream.

Author: weierophinney

README.md

@@ -14,9 +14,6 @@ This library provides utilities for:
 The `RequestHandlerRunner` will be used in the bootstrap of your application to
 fire off the `RequestHandlerInterface` representing your application.
 
-If you are developing an async application, you will more than likely not want
-to use this package.
-
 ## Installation
 
 Run the following to install this library:

docs/book/intro.md

@@ -10,6 +10,3 @@ This component provides  utilities for:
 
 The `RequestHandlerRunner` will be used in the bootstrap of your application to
 fire off the `RequestHandlerInterface` representing your application.
-
-If you are developing an async application, you will more than likely not want
-to use this package.