Vectors can be marshalled/unmarshalled
Deques can be marshalled/unmarshalled
Fixed typo in SortedSet#marshal_dump/#marshal_load spec
Remove some unneeded blank lines from Yardoc
Remove useless Code Climate badge from README
#eql? can return immediately if argument is 'self'
Remove unnecessary indirection when extending IO. Add doc for IO#to_list
Remove an unneeded check from Vector#slice and SortedSet#slice