Fix Haddock generation

Due to wrong Haddock comment usage, the documentation could not be built. See [Hackage build log](http://hackage.haskell.org/package/resource-effect-0.1.0/reports/1/log) for the demonstration of this issue.

The problem is that you were trying to document each constructor parameter individually. This is not allowed. The only way to do something like this is to use a record and document the fields. Please refer to [Haddock documentation](http://www.haskell.org/haddock/doc/html/ch03s02.html)