add nokogiri to gemfile

is there a reason why this isn't in there? i was getting this error without it...
```
huynhs@~/Projects/wraith ~> rake

rake aborted!
cannot load such file -- nokogiri
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/page.rb:1:in `require'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/page.rb:1:in `<top (required)>'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/http.rb:2:in `require'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/http.rb:2:in `<top (required)>'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/tentacle.rb:1:in `require'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/tentacle.rb:1:in `<top (required)>'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/core.rb:3:in `require'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone/core.rb:3:in `<top (required)>'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone.rb:2:in `require'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/gems/anemone-0.7.2/lib/anemone.rb:2:in `<top (required)>'
/Users/huynhs/Projects/wraith/lib/wraith_manager.rb:3:in `require'
/Users/huynhs/Projects/wraith/lib/wraith_manager.rb:3:in `<top (required)>'
/Users/huynhs/Projects/wraith/Rakefile:3:in `require'
/Users/huynhs/Projects/wraith/Rakefile:3:in `<top (required)>'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/bin/ruby_executable_hooks:15:in `eval'
/Users/huynhs/.rvm/gems/ruby-1.9.3-p385/bin/ruby_executable_hooks:15:in `<main>'
(See full trace by running task with --trace)
```