Use String as key

1.9.3はsymbolとstring両方で取れるが、2.0.0はstringでしか取れない
両方で使えるように、stringで取る
Ruby2.0.0ではValueがStringでないと保存されない
Merge pull request #184 from sanemat/feature/option-restore

Ruby2.0.0でOptionのsave, restoreが出来るようにした
Add redcarpet.
Merge pull request #185 from hrysd/redcarpet

Add redcarpet.
Add default markup in admin/site/edit
Merge pull request #187 from rono23/add-default-markup

Add default markup in admin/site/edit
Upgrade sinatra, rake and rack
Remove ruby 1.8.7 support
Add ruby2.0 support
Temporally commit
Merge branch 'master' into active-record

Conflicts:
	Gemfile
	Gemfile.lock
	lib/lokka.rb
	lib/lokka/helpers/helpers.rb
	lib/lokka/models/category.rb
	lib/lokka/models/comment.rb
	lib/lokka/models/entry.rb
	lib/lokka/models/field.rb
	lib/lokka/models/field_name.rb
	lib/lokka/models/option.rb
	lib/lokka/models/site.rb
	lib/lokka/models/snippet.rb
	lib/lokka/models/tag.rb