Change main file to the building one

README.md

@@ -6,6 +6,7 @@ A Browser detector. Because sometimes, there is no other way, and not even good
 # Contents
 - [Overview](#overview)
 - [Use cases](#use-cases)
+- [Advanced usage](#advanced-usage)
 - [How can I help?](#contributing)
 
 # Overview
@@ -107,6 +108,12 @@ Thus, you can define OS or platform specific rules and they will have more prior
 
 More of API and possibilities you will find in the `docs` folder.
 
+# Advanced Usage
+By default, `require('bowser')` requires the pre-compiled file, which can
+include useless for you polyfills. In case you don't need that, you can choose
+using source file requiring bowser like that: `require('bowser/src/bowser`);
+Then you get ES2015 file, which is not precompiled and can be easier to debug.
+
 # Contributing
 If you'd like to contribute a change to bowser, modify the files in `src/`, then run the following (you'll need node + npm installed):