Rails dev tools

This is a collection of utilities used for Rails internal development. They aren't used by Rails apps directly.

• console drops you in irb and loads local Rails repos
• profile profiles Kernel#require to help reduce startup time
• line_statistics provides CodeTools module and LineStatistics class to count lines
• test is loaded by every major component of Rails to simplify testing, for example: cd ./actioncable; bin/test ./path/to/actioncable_test_with_line_number.rb:5