How to debug/test nginx-clojure handlers

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There are currently two methods available for debugging/testing nginx-clojure handlers. One is that we run a normal nginx instance with the jvm remote debugging option enabled. The other is to use the recommended subproject nginx-clojure-embed, which is very easy to use with IDEs and unit testing tools. Later we can do some enhancements

1. Add some code to several example projects to show how to use nginx-clojure-embed to debug/test handlers
2. Add more documentation to show more details about debugging/testing handlers with nginx-clojure-embed.
3. The binary dist of nginx-clojure-embed needs to compile more built-in nginx modules. Related to nginx-clojure-embed need be compiled with more built-in nginx c modules #288