Switch markdown processor to kramdown

Github appears to recommend kramdown
https://help.github.com/articles/migrating-your-pages-site-from-maruku

Additionally, kramdown appears to support tables:
http://kramdown.gettalong.org/syntax.html

Signed-off-by: Jordan Justen <jljusten@gmail.com>
Close img tag to avoid markdown warning message

Signed-off-by: Jordan Justen <jljusten@gmail.com>