- load and namespace the ext/mimemagic/Rakefile into the main Rakefile
- update test task to include ext as a prereq
- add the generated path.rb to clobber

and two fixes to ext/mimemagic/Rakefile

- more robust file load (gem dev vs gem install consistency)
- use squiggly HEREDOC to indent generated file properly

update the readme to match
add LICENSE and CHANGELOG to doc

add yardoc settings for doc writers