README.md: markdown fixes

small tweaks fixing some broken Markdown formatting in README
Enhancement: Improve installation process

redux now installs man pages in the first of the following locations:

0 use --mandir flag value if it exists
1 use MANDIR if it is set
2 use first non-empty path in MANPATH if it is set.
 This is equivalent to: $(echo $MANPATH | cut -f1 -d:) except that we skip empty fields.
3 use $(dirname redux)/../man if it is writable
4 use first non-empty path in `manpath` if there's one.
 This is equivalent to: $(manpath 2>/dev/null | cut -f1 -d:) except that we skip empty fields.
5 use '/usr/local/man'

Resolves: https://github.com/gyepisam/redux/issues/4
add install tests
Merge branch 'patch-1' of https://github.com/akavel/redux

A few tweaks to improve it.