no such file to load -- rd/rdfmt (LoadError)

./tdiary/rd_style.rb:17:in `require'
./tdiary/rd_style.rb:17
./tdiary.rb:375:in `require'
./tdiary.rb:375:in `load_styles'
./tdiary.rb:374:in `glob'
./tdiary.rb:374:in `load_styles'
./tdiary/defaultio.rb:110:in `initialize'
./tdiary.rb:849:in `new'
./tdiary.rb:849:in `initialize'
./tdiary.rb:1421:in `initialize'
./tdiary.rb:1657:in `initialize'
index.rb:44:in `new'
index.rb:44