* next init: Create supplied directory if it does not exist.
* next init: use mkdirp to init into nested dirs.
Picked mkdirp-then out of many alternatives. Same author & similar
dependencies to mz.
Now next init a/b/c works.
Related https://github.com/zeit/next.js/pull/136#discussion_r85543040
Should only exit `0` if the command was successful. The command refusing to execute should be considered a failure.
Also, this condition can be detected synchronously, no need to wait on the async existence check.
* Added next bootstrap command for starting a new project
* renamed bootstrap to init and check we are not in a dir called pages
* Removed extra empty line