[ Cabal ] Removed support for equivalence 0.2.4

The only difference between equivalence 0.2.4 and 0.2.5 was a missing
file in the tarball (see
https://bitbucket.org/paba/equivalence/commits/all).
[ Utils.Cluster ] Mini refactor

- Replaced 'forM' by 'forM_'.
- Using qualified name 'IntMap' instead of 'Map'.
- Removed unnecessary 'forall' keyword.
- Removed unnecessary pragmas.
[ issue 1283 ] Added missing type signatures