text: Title: some imports appear to be really really slow
  Body: Hello, 
  
  I found that some imports take quite a while, at least on my Mac laptop.  Specifically
  ```python
  from kaldi.asr import NnetLatticeFasterOnlineRecognizer
  ```
  takes over 7 seconds.  Is this just dynamically linking the relevant .so (on on mac .dylib) files?  
  
  On my system `libkaldi-nnet3.dylib` is 17MB, which appears the largest of all the .dylib files, but still this is not a lot to load from disc (maybe the linking takes long?).   