Add the ability to set configs in ~/.scatterconfig

Uses YAML
Use config to set the default directory

Let's .scatterconfig override the default directory

Example usage:

```
directory: "/Users/evan/.otherdeploys"
```
Allow aliases to be defined in .scatterconfig

Example usage:

```
aliases:
  wp: "-s wp"
  print: "-s print"
```
Ruby will automatically return nil if the key doesn't exist
Add save, set and show methods to Config

save: Overwrite the config file with new settings, accepts a hash
set: Set a single key to a single value
show: Show YAML versio of the whole config, or the config for a single key
Add alias and config commands
Specify where the config file is stored
Add config and alias info to readme
Scatter now has a config file, call it 0.2.0