- Cosmetic: replace tabs with blanks, strip trailing white space,
and update copyright headers with spec-cleaner.

- Update th-abstraction to version 0.2.8.0.
## 0.2.8.0 -- 2018-06-29
* GADT reification is now much more robust with respect to `PolyKinds`:
* A bug in which universally quantified kind variables were mistakenly
flagged as existential has been fixed.
* A bug in which the kinds of existentially quantified type variables
were not substituted properly has been fixed.
* More kind equalities are detected than before. For example, in the
following data type:
```haskell
data T (a :: k) where
MkT :: forall (a :: Bool). T a
```
We now catch the `k ~ Bool` equality.
* Tweak `resolveTypeSynonyms` so that failing to reify a type constructor
name so longer results in an error. Among other benefits, this makes
it possible to pass data types with GADT syntax to `normalizeDec`.
## 0.2.7.0 -- 2018-06-17
* Fix bug in which data family instances with duplicate occurrences of type
variables in the left-hand side would have redundant equality constraints
in their contexts.