remove hoptoad

Hoptoad is deprecated. See
https://github.com/thoughtbot/hoptoad_notifier
remove ruby-debug
remove debugger gem
remove yajl-ruby, json
remove deprecated glueoutputbuf option
ignore spec/stdout
remove airbrake
remove yajl-ruby dependency
ignore test files
remove redgreen, commoand? from Rakefile
update gemspec

* require ruby 2.0
* require resque 1.25
* remove require rubygems
* use https rubygems source
* remove development version dependencies on mocha, rack-test
cleanup Rakefile
remove init.rb, rails/initr.b
remove support for deprecated module, whitespace
remove unnecessary .first