Using “tgmath.h”.
Merge pull request #2 from JanX2/jan/tgmath

Using “tgmath.h”.
moved marker prefix scanning into category
moved image scanning into scanner
builds, but in flight DTMarkdownParser:198
fixed tests, refactoring
refactor a bit for readability
Added two heading unit tests
Merge branch 'od/issue_1' into develop
Merge remote-tracking branch 'refs/remotes/Cocoanetics/develop' into jan/demo