removed old hmac.rb file, adopted tests for new feature
load hmac folder in simple_auth.rb
Middlware DSL & refactoring

With the new middleware dsl some major changes has occured.

First of all HMAC is no longer a Class and represent a Module now.
Under this new Module 2 Classes were created:
  - Middleware
  - Config

The middleware class is the interface to the rack api (#call method)
On initializing (when using 'use ...') a HMAC Config object is instantiated.
The instance variables of this config object (tolerance, stepsize, secret ...) is
populated via yielding the middleware block into the config object

Open TODOS:
  - refactor Middleware#request_data
  - add error handling to config object (wrong dsl directive should output nice error)
add error handling for trying to 'run' Rack::SimpleAuth::HMAC::Middleware as Rack Application
add dsl error handling
Test Folder changed

Changed the structure of test folder (hmac subfolder added where hmac tests live now)
Added tests for new features:
  - DSL
  - DSL error handlin
  - Middlware run as Rack Application error handling
delete log folder from git repo
Logger.log - create logfolder if nonexistent
adopted cleanup path
ignore linelength till 150
rubocop optimizing - add comments, if modifier usage etc...
Middleware#log - don't use hash_array param, can be retreived via Middleware#allowed_messages
updated README