Added a shellcheck(1) man page

The manual is mainly a copy/paste from the current documentation. It is
builded with pandoc, and written in markdown.

closes #50
Warn about 'i=i+1' and 'i=i + 1'
Minor performance tweaks (~10% improvement)
Merge branch 'man_page' of https://github.com/Dridi/shellcheck into manpage
Tweaked man page format
Merge branch 'manpage'
Parser: allow subshell function definitions
Fixed ${!var} not counting as reference of var
expanded cabal file
Merge pull request #61 from cheecheeo/master

expanded cabal file
Warn about abused char classes, such as [10-15] and [:digit:]
Don't warn about quotes in variables for eval
Allow '# shellcheck disable=SC1234' to ignore by code.
Warn about 'cd $f; foo; cd ..' loop antipattern.
man page: Added Directives section
Cleaned up cabal file to make 'cabal check' pass.
Stable version 0.3.0
Added Mac OS instructions with brew (relates #11)

Un-Markdown text
Merge pull request #67 from michaelsanford/master

Added cabal setup instructions for Mac OS X to README
Parse but warn about "else if"