Immutable*Collection*.Builder methods can't begin with 'get'

```
@AutoValue
abstract class MyClass {
abstract ImmutableList getBlobs();
Builder builder() {
return new AutoValue_MyClass.Builder();
}
@AutoValue.Builder
abstract static class Builder {
abstract ImmutableList.Builder getBlobsBuilder();
abstract MyClass build();
}
}
```

Results in:

```
Error: ... : Method without arguments should be a build method returning MyClass or a getter method with the same name and type as a getter method of MyClass
```

Currently, you must name `getBlobsBuilder()` as `blobsBuilder()` to function. As every other builder method supports _bean_ style setters, the collections builders should support _bean_ style getters.