fix: match only against the end of a file path. (#654)

Author: pat

lib/twilio-ruby/rest.rb

@@ -5,7 +5,7 @@
 end
 
 Dir[File.join(__dir__, 'rest/*.rb')].sort.each do |file|
-  require file.gsub('.rb', '_base.rb') unless file.end_with?('client.rb') || file.end_with?('_base.rb')
+  require file.gsub(/\.rb$/, '_base.rb') unless file.end_with?('client.rb') || file.end_with?('_base.rb')
   require file
 end