v0.3.0

Added

• Added part_one and part_two attribute macros for annotating the puzzle solvers
  • Can be used to indicate the correct answer to the puzzle once it has been solved, like so: #[part_one(answer = "42")]
• Added test_solutions! macro for generating tests that test the solutions against their correct answers

Removed

• Removed test_part_one_solution! and test_part_two_solution! in favor of test_solutions!