Replace state transition helper functions with optimized versions.

[g-r-a-n-t]

What is wrong?

In ethereum/trinity#1918, we copied https://github.com/protolambda/eth2fastspec into our repo and made the minimal changes required for compatibility. A major improvement in code quality would be to replace the existing helper functions with their optimized versions.

How can it be fixed

• replace existing helper functions with optimized versions
• raise ValidationErrors instead of AssertionErrors when validation fails Eth2fastspec validation cleanup. trinity#1977
• parameterize config values, instead of hardcoding Altona values Eth2fastspec config cleanup. trinity#1967
• ensure that spec tests are running on optimized helper functions