Fix sample code of Enumerable#one?

オリジナルがrdocのドキュメントだと思うので、rodcに合わせて修正しました。
Merge pull request #59 from utenmiki/enumerable

Fix sample code of Enumerable#one?
Add Array#to_h and Enumerable#to_h since 2.1.0
Add Binding#local_variable_get, #local_variable_set and #local_variable_defined? since 2.1.0
Add Object#singleton_method since 2.1.0
Add Fixnum#bit_length and Bignum#bit_length since 2.1.0
Remove curses since 2.1.0
Add Exception#cause since 2.1.0
Update IO#seek and add IO::SEEK_DATA, IO::SEEK_HOLE
Add Proccess.#argv0 and .#setproctitle since 2.1.0
Add String#scrub and #scrub! since 2.1.0
Fix typo
Update Array#to_h and Enumerable#to_h
Update String#scrub and #scrub argument