issue: https://github.com/gibiansky/IHaskell/issues/236

To verify functionality, paste the following into a code block in
IHaskell.

```
:ext TemplateHaskell
import Language.Haskell.TH
import Control.Lens
data Foo a = Foo { _bar :: Int, _baz :: Int, _quux :: a }
makeLenses ''Foo
:ty baz
```