Include?, Map, better Each

Enum existence with .include?, .map, better .each and matching rspec test coverage
Existing .each tests pass.

Examples of new features in the following tests:

```ruby
describe '.include?' do

      it 'returns true for an Enum that is defined' do
        class TestEnumToInclude
          extend Enumb
          enumerator :Alpha => 1
          enumerator :Beta => 2
          enumerator :Charlie => 3
          enumerator :Echo => 4
        end
        x = TestEnumToInclude.Beta

        class TestEnumTonNotInclude
          extend Enumb
          enumerator :Alpha => 5
          enumerator :Beta => 6
          enumerator :Charlie => 7
          enumerator :Echo => 8
        end
        y = TestEnumTonNotInclude.Beta

        expect(TestEnumToInclude.include?(x)).to be_true
        expect(TestEnumToInclude.include?(y)).to be_false
      end

    end

    describe '.map' do

      it 'returns Array of enums' do
        class TestEnumToInclude
          extend Enumb
          enumerator :Alpha => 1
          enumerator :Beta => 2
          enumerator :Charlie => 3
          enumerator :Echo => 4
        end
        expect(TestEnumToInclude.map).to match_array [TestEnumToInclude.Alpha, TestEnumToInclude.Beta, TestEnumToInclude.Charlie, TestEnumToInclude.Echo]
      end

    end

    describe '.enums' do

      it 'returns Array of enums' do
        class TestEnumToInclude
          extend Enumb
          enumerator :Alpha => 1
          enumerator :Beta => 2
          enumerator :Charlie => 3
          enumerator :Echo => 4
        end
        expect(TestEnumToInclude.map).to match_array [TestEnumToInclude.Alpha, TestEnumToInclude.Beta, TestEnumToInclude.Charlie, TestEnumToInclude.Echo]
      end

    end
```