Relax dependency on semigroups which is overly strict
Qualify imports of Numeric.Natural using -XPackageImports

Otherwise we can get failures like this.

Test suite doctests: RUNNING...
expected:
 but got:
          <no location info>:
              Ambiguous module name `Numeric.Natural':
                it was found in multiple packages: semigroups-0.8.4.1 nats-0.1
Examples: 718  Tried: 705  Errors: 0  Failures: 1
Test suite doctests: FAIL