Add Specialized modules and more docs

  - Specialized avoids type classes at expense using more modules
  - added better documentation (only in Specialized for now)
  - should Generic be deprecated?
Remove dependency of tests on Cabal

Got fed up with being dependent on the large library, as well as the
various conflicts that often occur because the version of Cabal used by
the test doesn't coincide with the version of Cabal used by
cabal-install.
Add predefined link flags to .cabal

  - now links to Netlib Blas by default
  - predefined flags are added for common use cases
  - still needs some manual intervention
Update .travis.yml

  - always show output of tests on Travis
  - run tests in tarball as well to avoid missing modules

Note: tried to test against OpenBLAS as well but Travis failed with
"Illegal instruction" even though the linking went successfully.  Unable
to reproduce locally on virtual machine.
Update readme and package description
Use Specialized to implement Generic