attempt to pass doc through a pager
remove buggy code that tries to use `more` for paging `wp help`

* Windows throws an unexpected exit status when trying to use `less`
* more doesn't have an '-r' flag
Merge branch 'master' into help-pager

(should fix unrelated build errors)
always pass docs through WP_CLI::colorize()
help: remove unused find() utility
Merge pull request #552 from wp-cli/help-pager

Make `wp help` use a pager