- fixed a bug that did not discard strings with control characters
between 0x10 and 0x1f
- added termination proofs for two important loops
- made get_ref() constexpr

let the makefile choose the correct sed

- improved documentation

- improved parser performance by avoiding a copy of the result value

- added error macros to exclude unsupported compilers

- replaces some raw loops by std algorithms
- used std::advance where possible

Update hexify to use array lookup instead of ternary (#270)