--fix doesn't modify my file

I imagine I'm doing something wrong here, but I'm not sure what:

```
$ gem install --pre puppet-lint -v 0.4.0.pre1
Fetching: puppet-lint-0.4.0.pre1.gem (100%)
Successfully installed puppet-lint-0.4.0.pre1
1 gem installed
Installing ri documentation for puppet-lint-0.4.0.pre1...
Installing RDoc documentation for puppet-lint-0.4.0.pre1...
$ puppet-lint --version
Puppet-lint 0.4.0.pre1
$ puppet-lint -f file.pp
WARNING: class not documented on line 1
ERROR: tab character found on line 17
ERROR: tab character found on line 19
ERROR: trailing whitespace found on line 14
ERROR: two-space soft tabs not used on line 17
ERROR: two-space soft tabs not used on line 19
WARNING: indentation of => is not properly aligned on line 17
$ puppet-lint --fix file.pp
WARNING: class not documented on line 1
ERROR: tab character found on line 17
ERROR: tab character found on line 19
ERROR: trailing whitespace found on line 14
ERROR: two-space soft tabs not used on line 17
ERROR: two-space soft tabs not used on line 19
WARNING: indentation of => is not properly aligned on line 17
$ svn diff
$
```

In short, nothing's being changed in my input file.  I'll attach the input so you can see what I'm doing (in short: there's plenty wrong with it).