requires bundler
cleans up configuration class

- removes asset_host_protocol
- renames asset_formats to asset_types
- simplifies asset_types hash `{ext: 'content_type'}`
- performance tweaks and other clean up
moves the assets folder back to spec/support where it belongs
finalizes config defaults & works out remaining quirks
adds minitest-spec-context gem to testing stack
ensure sprockets environment is set up properly
refactors rack middleware

- smaller foot print
- define routes for all registered sprockets.mime_types
- clean up specs with proper context
requires minitest-spec-context gem
removes sprockets-helpers

- ensures Rack::ClassyAssets is loaded properly
- removes dependency on sprockets-helpers
- starts new Sinatra::ClassyAssets::Helpers module to replace
  sprockets-helpers
- cleans up specs a bit

WIP
implements asset_path in sprockets context

enables use of asset_path method inside of assets (e.g. asset_path('image.png') returns '/assets/image.png')
adds TODO
adds slim to testing stack
breaks Configuration class out into it's own file

and moves specs as well
adds utility methods in top level ClassyAssets module

with specs
require slim to enable use in apps under spec
fleshes out behaviour of stylesheet_tag and javascript_tag helpers
Bump to 0.4.0