The Big Jekyll Command Cleanup

So I've decided to dedicate some time to cleaning up the `bin/jekyll` binary.

This branch is pretty much finished.

Commands are more intuitive thanks to the useful help output. There are three distinct subcommands at the minute; `build`, `serve` and `import`.

## Build

Builds the jekyll site, has some options:

  *  `-w, --watch` will watch for changes and rebuild when they're detected
  * `--lsi` will build using LSI for improved related posts

## Serve

Serves the built jekyll site, has some options:

### Passed to the pre `build` command before serving

  * `-w, --watch` will watch for changes and rebuild when they're detected
  * `--lsi` will build using LSI for improved related posts

### Passed to the `serve` command for serving

  * `-p, --port` port to listen on
  * `-h, --host` host to bind to
  * `-b, --baseurl` base URL

## Import/Migrate

Imports blog posts from another platform using the migrators.

  * `--file` file to migrate from
  * `--dbname` database name to migrate from
  * `--user` user to use when migrating
  * `--pass` password to use when migrating
  * `--host` host address to use when migrating