Fix race conditions in tests, change travis rbx name

.travis.yml

@@ -1,5 +1,5 @@
 rvm:
   - 1.8.7
   - 1.9.3
-  - rbx-2.0
+  - rbx
   - jruby

test/test_rack_server.rb

@@ -68,6 +68,8 @@ class TestRackServer < Test::Unit::TestCase
 
     hit(['http://localhost:9998/test'])
 
+    stop
+
     if exc = @checker.exception
       raise exc
     end
@@ -80,6 +82,8 @@ class TestRackServer < Test::Unit::TestCase
 
     hit(['http://localhost:9998/test/a/b/c'])
 
+    stop
+
     assert_equal "/test/a/b/c", input['PATH_INFO']
   end
 
@@ -95,6 +99,8 @@ class TestRackServer < Test::Unit::TestCase
 
     hit(['http://localhost:9998/test'])
 
+    stop
+
     assert_equal true, closed
   end