#557: README.md, update 'linux packages' subsection
#557: README.md, add colons in 'linux packages' subsection
#557: README.md, various typos for 'linux packages' subsection
#557: README.md, typo fix for 'linux packages' subsection
Merge pull request #558 from jeff1evesque/doc_linux_packages

#557: Documentation: Update 'Linux Packages' Subsection