htmlprocessor.js can strip unparsed comment blocks

If you pass an option stripUnparsed === true, comment blocks will be removed (and their internal content remain) if the type doesn't exist or target doesn't match
don't split undefined (no target)
move _strip out of blockTypes
oops.. split undefined again
add strip test, convert to 'options.strip' from 'options.stripUnparsed'
tests for multiple comma-separated targets
update Readme (still need examples)
Merge pull request #19 from maxbates/patch-2

htmlprocessor.js - comma-separated targets, strip unparsed comment blocks