Fix route requirements bug

This was a bug introduced by commit 9f4ba67. The commit
replaces `options[:route_options].clone.merge(...)` with
`options[:route_options].clone.reverse_merge(...)`.
That causes disappear of the requirements in namespace.

Author: darren987469

CHANGELOG.md

@@ -9,6 +9,7 @@
 * Your contribution here.
 * [#1776](https://github.com/ruby-grape/grape/pull/1776): Validate response returned by the exception handler - [@darren987469](https://github.com/darren987469).
 * [#1787](https://github.com/ruby-grape/grape/pull/1787): Add documented but not implemented ability to `.insert` a middleware in the stack - [@michaellennox](https://github.com/michaellennox).
+* [#1788](https://github.com/ruby-grape/grape/pull/1788): Fix route requirements bug - [@darren987469](https://github.com/darren987469), [@darrellnash](https://github.com/darrellnash).
 
 ### 1.1.0 (8/4/2018)
 

lib/grape/endpoint.rb

@@ -200,7 +200,7 @@ def prepare_version
     end
 
     def merge_route_options(**default)
-      options[:route_options].clone.reverse_merge(**default)
+      options[:route_options].clone.merge(**default)
     end
 
     def map_routes