ekmett/lens — pull request #368 by jwiegley (2013-12-01 10:21:08+00:00)
Title: Add a makeClassy_ lens builder

`makeClassy_` makes lenses and traversals for a type, and create a class when
the type has no arguments. Works the same as 'makeClassy' except that:

- it expects that record field names do not begin with an underscore
- all record fields are made into lenses
- the resulting lens is prefixed with an underscore.