Stabilize Code for Release

[aerkiaga]

Stabilize the code enough that it's suitable for casual/exploratory use. To this end, we'll resort to a combination of fuzz testing and mutation testing.

nacre_kernel:

• Pass fuzz test.
• 80 % mutation score.

nacre_parser:

• Pass fuzz test.
• 80 % mutation score.

nacre_ast:

• 80 % mutation score.

nacre_compiler

• Pass fuzz test.
• 80 % mutation score.