Wordpress deployment changes

- Do not generate wp-config.php on each deploy
- Print wordpress core version at start
- Print wordpress cli version at start
Install wordpress cli from tags, not master
Add method to uninstall wp cli
Specify wordpress cli version in config

Now its possible to install a specific wp-cli utility by
adding an extra config option into deployment file.

Example:

```
wordress:
  cli: 0.9.1
```

Or install from master:

```
wordpress:
  cli: master
```

By default, shuttle will install from latest git tag.