Refactored, added tests and made int parser faster

src/combinators/atomic_combinators.rs

src/combinators/common/characters/mod.rs

src/combinators/common/characters/whitespace.rs

src/combinators/common/integers/ints.rs

src/combinators/common/integers/ints.txt

src/combinators/common/integers/ints_basic.rs

src/combinators/common/integers/mod.rs

src/combinators/common/mod.rs

src/combinators/mod.rs

src/combinators/non_atomic_combinators.rs

src/combinators/other/brainflakes/brainflakes_parser.rs

...nators/other/brainflakes/brainflakes_parser_components.rs

...ators/other/brainflakes/example_programs/brainflakes_1.bf

...inators/other/brainflakes/example_programs/hello_world.bf

src/combinators/other/brainflakes/mod.rs

src/combinators/other/expressions/expression.rs

src/combinators/other/expressions/expression.txt

src/combinators/other/expressions/mod.rs

src/combinators/other/mod.rs

src/combinators/tests/mod.rs