README: adapt all README files to markdown
README: change all README files extenstion to markdown
README: use plain text for URLs as Github automatically convert them
README: use underlines instead of hash-signs for h1 & h2 headers
README: remove all language identifiers from code blocks
README_linux: small correction on how to run sclang
readme: osx - remove 10.8 warning (re 29681f4)
Merge branch 'master' into topic/markdown_for_README_files

Conflicts were resolved in:
	README_LINUX.txt
	README_OS_X.txt
	README_WINDOWS.md
Merge pull request #890 from gusano/topic/markdown_for_README_files

Topic/markdown for readme files