Update specs & travis-ci

Added Rakefile
Using new sinatra-contrib helpers 
Recovered specs helpers from deprecated sinatra-test-helper

There is 2 specs not working with HEAD request and I don't see why, if you have any clue :

```
Failures:

  1) Sinatra::AdvancedRoutes HTTP HEAD activation is able to deactivate routes from the outside
     Failure/Error: browse_route(verb, "/foo").should_not be_ok
       expected ok? to return false, got true
     # ./spec/sinatra/advanced_routes_spec.rb:24:in `block (5 levels) in <top (required)>'

  2) Sinatra::AdvancedRoutes HTTP HEAD activation is able to deacitvate routes from a before filter
     Failure/Error: browse_route(verb, "/foo").should_not be_ok
       expected ok? to return false, got true
     # ./spec/sinatra/advanced_routes_spec.rb:31:in `block (5 levels) in <top (required)>'
```