Update ruby-sinatra to 1.4.7.

= 1.4.7 / 2016-01-24

* Add Ashley Williams, Trevor Bramble, and Kashyap Kondamudi to team Sinatra.

* Correctly handle encoded colons in routes. (Jeremy Evans)

* Rename CHANGES to CHANGELOG.md and update Rakefile. #1043 (Eliza Sorensen)

* Improve documentation. #941, #1069, #1075, #1025, #1052 (Many great folks)

* Introduce `Sinatra::Ext` to workaround Rack 1.6 bug to fix Ruby 1.8.7
  support. #1080 (Zachary Scott)

* Add CONTRIBUTING guide. #987 (Katrina Owen)

(taca)