Move build script to bash

/cc #1145

.travis.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+
+echo "Running sinatra tests..."
+bundle install --jobs=3 --retry=3
+bundle exec rake
+
+echo "Running sinatra-contrib tests..."
+cd sinatra-contrib
+bundle install --jobs=3 --retry=3
+bundle exec rake

.travis.yml

@@ -24,9 +24,7 @@ rvm:
   - jruby-9.1.0.0
   - jruby-head
 
-script:
-  - bundle exec rake
-  - cd sinatra-contrib && bundle install --jobs=3 --retry=3 && bundle exec rake
+script: .travis.sh
 
 sudo: false