properly handle options and type inference in macros

[davidhewitt]

Followup to #110

• Removes the otherwise breaking change to require explicit types on integers
• Moves Option<T> specialisation into an earlier phase of the conversion so that it can correctly work on other T which are specialised (such as primitive integers)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 99.66443% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/macros/mod.rs	99.63%	1 Missing ⚠️

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