Added a first-pass attempt at a SlateWriter.
It can be used by changing the config.format to 
include `:slate`
Changed slate extension to be markdown's ext
Pulled the example mustache content in to the 
index slate file.
Added a has_response_body? helper for mustache
file to check if it should output the response 
body headers.
Added a conditional around response_body output.
Conditional output of endpoint parameters.
Added a pretty JSON printer method to make the 
slate output more reader-friendly.
Updated slate index to include endpoint 
explanation.
Merge pull request #1 from xyzjace/slate_template

Added a first-pass attempt at a SlateWriter.