This PR renames the CLI and config files to `vercel`.
https://vercel.com/blog/zeit-is-now-vercel
### Complete
- [x] Help menus and error messages should print cli name from `package.json`
- [x] `now.json` => `vercel.json`
- [x] `.nowignore` => `.vercelignore`
- [x] `~/.now` => `~/.vercel`
- [x] `<project>/.now/project.json` => `<project>/.vercel/project.json`
### TODO
I'm going to do the remaining work in a follow-up PR:
- [ ] `<project>/.now/cache` => `<project>/.vercel/cache` (Runtimes sometimes use this)
- [ ] `NOW_*` special cased environment variables
- [ ] `*.now.sh` special cased url suffix
* Added two example error links
* More messages added
* Even more cool stuff
* Removed useless assignments
* Weird stuff removed
* Fixed exiting
* Added missing space
* Added another error message
