text: Title: Using custom model with different input size? (rgb: True)
  Body: I've successfully trained my own model, thank you so much for the guidance there, but now when I am trying to use the model I made with `rgb: true` (making it have an input of 3 channels) I get errors for size mismatches:
  
  ```
  RuntimeError: Given groups=1, weight of size [32, 3, 3, 3], expected 
   input[1, 1, 64, 256] to have 3 channels, but got 1 channels instead
  ```
  
  This may be due to the downloaded model, or something? I played with `download_enabled` and removing the downloaded model, that gives this error:
  
  ```
  FileNotFoundError: Missing ./ocr_model/craft_mlt_25k.pth and downloads disabled
  ```
  
  How do I use the reader **only using** my network? or am I trying to do something that doesn't make any sense? If my training is making great predictions, I'm confused on why I need another model?
  
  ```py
  reader = easyocr.Reader(
      ['en'], 
      # here's where my custom_model.pth file is
      model_storage_directory="./ocr_model",  
      # here's where my custom_model.py and custom_model.yaml live
      user_network_directory='./ocr_network',   
      recog_network='custom_model'
  )
  reader.readtext('test.jpg')
  ```
  
  I believe I set `custom_model.yaml`  up properly:
  ```yaml
  network_params:
    input_channel: 3
    output_channel: 256
    hidden_size: 256
  imgH: 64
  lang_list:
           - 'en'
  character_list: 0123456789!"#$%&'()*+,-./:;<=>?@[\]^_`{|}~ ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz
  ```
  
  ## EDIT
  
  Doing the exact same training but with `rgb: False` and everything works, woo! am I missing  out on much without rgb? 