Write tests

simple_parse relies on automatically generated code and unsafe implementations that have been manually validated to be safe.

It would provide an extra sense of "security" if we also had tests testing a bunch of different edge cases e.g. :

- Invalid lengths (Too short, too big)
- Invalid contents (Bad utf8 for strings, 0 for NonZero, etc...)
- Invalid alignment for references
- Etc...

This will be a pain to write manually so macros will probably have to be create to test each default implementation and then test the derived code containing those default impls