literate detect

bin/detect

 #!/usr/bin/env bash
-# bin/detect <build-dir>
+
+# This script serves as the 
+# [**Python Buildpack**](https://github.com/heroku/heroku-buildpack-python) 
+# detector. 
+# 
+# A [buildpack](http://devcenter.heroku.com/articles/buildpacks) is an 
+# adapter between a Python application and Heroku's runtime.
+
+# ## Usage
+# Compiling an app into a slug is simple:
+# 
+#     $ bin/detect <build-dir> <cache-dir>
 
 BUILD_DIR=$1