v0.3.0

Breaking

• Bump MSRV (minimal supported Rust version) to 1.54

Added

• Add raw_input and into_raw_input to non-bool *Lit types
• Add impl From<*Lit> for pm::Literal (for non-bool literals)
• Add impl From<BoolLit> for pm::Ident

Fixed

• Fix link to reference and clarify bool literals (#7)

Internals

• Move lots of parsing code into non-generic functions (this hopefully reduces compile times)
• To implement [into_]raw_input for integer and float literals, their
  internals were changed a bit so that they store the full input string now.