Make listing JS files in the import map a predictable order (closes #108)

Author: dhh

lib/importmap/map.rb

@@ -149,7 +149,7 @@ def module_path_from(filename, mapping)
     end
 
     def find_javascript_files_in_tree(path)
-      Dir[path.join("**/*.js{,m}")].collect { |file| Pathname.new(file) }.select(&:file?)
+      Dir[path.join("**/*.js{,m}")].sort.collect { |file| Pathname.new(file) }.select(&:file?)
     end
 
     def absolute_root_of(path)