Removed dependency on `lens-family`

@k0001 gave me the neat idea of just redefining the `Lens'` type synonym
internally and not exporting it.  This has three advantages:

* It removes the dependency on `lens-family`
* It cleans up type inference, by expanding out to an unqualified type instead
  of 'Lens.Family.LensLike ...`
* This trick can also be used for `Iso'`s, too, without depending on `lens`