FIPS compatibility

[fjarri]

Fixes #4

• Fixed some comments in pseudoprimes.rs
• Added LucasCheck::Regular to match what's described in FIPS-186.5 Section B.3.3
• Flattened the logic in lucas_test() to make it easier to understand when the checks are applied
• Simplified test structure in lucas.rs
• Added hazmat::minimum_mr_iterations() with the recommended formula from FIPS
• Added fips_is_prime_with_rng() and fips_is_safe_prime_with_rng()

Is there a better way to organize the FIPS preset? A fips submodule? Or just prefixes/suffixes? Should we provide a corresponding prime-generation function, or just have users rely on sieve_and_find()? Although maybe we should push it to when we're dealing with #62.

[codecov]

Codecov Report

Attention: Patch coverage is 95.40230% with 16 lines in your changes missing coverage. Please review.

Project coverage is 98.60%. Comparing base (ad4f439) to head (2a10f75).

Files with missing lines	Patch %	Lines
src/presets.rs	91.22%	10 Missing ⚠️
src/hazmat/lucas.rs	97.14%	3 Missing ⚠️
src/hazmat/float.rs	97.22%	2 Missing ⚠️
src/hazmat/miller_rabin.rs	98.24%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #72      +/-   ##
==========================================
- Coverage   99.47%   98.60%   -0.87%     
==========================================
  Files          11       12       +1     
  Lines        1512     1721     +209     
==========================================
+ Hits         1504     1697     +193     
- Misses          8       24      +16     

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