Performance for German?

Hi,
I want to use this tool to detect and correct grammatical mistakes in German. 

```
from nlprule import Tokenizer, Rules
tokenizer = Tokenizer.load("de")
rules = Rules.load("de", tokenizer)

t1 = "Ich habe eine Hund."
rules.correct(t1) 
```
This returns the string without any corrections (but it should,ideally, change "eine" to "einen").
