Add support for currently active page and tracking `heroku_session`

* Add middleware for gathering request data
* Track active page by exact url (regression)
* Support domain override for local site development
* Refactor into multiple classes
Refactor link behavior into Fuji::Link object
update Gemfile.lock
remove shorthand header method
update gem authors
Add Fuji options hash with optional Railtie

* Set config with "config.fuji_options = {}" in Rails
* Set config with "Fuji.options = {}" in Rack app
* Call with "Fuji::Header.render request"
* Fuji::Renderer abstract class handles core view logic
Green tests
Update README.md
Update style path
Add custom header subclass
Add Fuji::CustomHeader to README
remove a duplicate test
fix typo in readme
test for default and custom css classes
Merge pull request #5 from heroku/refactor

Refactor for 0.2