use new `wp cli` command
adapt template for new docs format

Kramdown is needed for definition lists.

see wp-cli/wp-cli#551
read docs from 'longdesc' property, instead of looking for doc files
build for 0.11-beta
point old commands to new commands
don't clear /commands/ directory when generating
update docs for 'wp cli'
space out the definition lists a little
switch to Kramdown syntax for fenced code blocks
merge release-0.11 branch into master