Test from sinatra in path and remove the "master" test

This means we'll always be testing the latest version of sinatra, no matter what.

Including any PRs sent to both projects, to ensure compatibility.

sinatra-contrib/Gemfile

@@ -2,10 +2,9 @@ source "https://rubygems.org" unless ENV['QUICK']
 gemspec
 
 gem 'mustermann', github: 'sinatra/mustermann'
-gem 'sinatra', github: 'sinatra/sinatra'
+gem 'sinatra', path: '..'
 
 group :development, :test do
-
   platform :jruby do
     gem 'json'
     gem 'rdoc'
@@ -35,8 +34,8 @@ end
 
 # Allows stuff like `tilt=1.2.2 bundle install` or `tilt=master ...`.
 # Used by the CI.
-repos = { 'sinatra' => 'sinatra/sinatra', 'tilt' => 'rtomayko/tilt', 'rack' => 'rack/rack' }
-%w[sinatra tilt rack].each do |lib|
+repos = { 'tilt' => 'rtomayko/tilt', 'rack' => 'rack/rack' }
+%w[tilt rack].each do |lib|
   dep = (ENV[lib] || 'stable').sub "#{lib}-", ''
   dep = nil if dep == 'stable'
   dep = {:github => repos[lib], :branch => dep} if dep and dep !~ /(\d+\.)+\d+/