Merge pull request #54 from Chris00/master

Default language for code & code stylist
fix: list items with paragraphs were not treated properly when starting with a minus (-) or a (+)
fix markdown output for lists containing paragraphs
version 0.7.2
change default value of argument `paragraph` (to `true`) for function `of_string`
change test.ml to work with omd 0.7.2
It was broken because a default value of a parameter has changed for `Omd.of_string`
fix #55
version 0.7.3
(0.7.4) fix #58

fix markdown output for non-references that look like references
Update README.md
fix #60

fix: not enough prefix spaces in backquote-defined code blocks inside list items

Thanks @Chris00.

(_oasis: omd 0.7.5)
fix #61
Test Omd.of_string(Omd.to_markdown md) = md
Merge pull request #64 from Chris00/round_trip

Test Omd.of_string(Omd.to_markdown md) = md
Remove trailing white space.
Remove one newline after Br.

Address https://github.com/pw374/omd/issues/67 (not sure it is
completely solved yet).