Fix Windows problem when init and edit

### homestead init
Windows doesn't have `$_SERVER['HOME']`. Instead we use Windows `%AppData%` variable, like most other Windows application do. One of advantage is the homestead configuration can sync to server when a user logged into Windows Server domain.

The default `%AppData%` mapping to
- `C:\Users\{username}\AppData\Roaming` in Windows Vista or higher
- `C:\Documents and Settings\{username}\Application Data` in Windows XP

### homestead edit
In Windows, `start` is similar command to open a file with default application.