function in jsngram.text2 module
Description
Normalize a text file or files in a directory including subdirectories. 
Uses normal_text for Unicode normalization. 
      
Example
jsngram.text2.normalize_texts('/scratch/a.txt', '/scratch/b.txt')
jsngram.text2.normalize_texts('/scratch/c', '/scratch/d')
jsngram.text2.normalize_texts('/scratch/e')
      
    Usage
jsngram.text2.normalize_texts(src, dest=None)
Normalize text files at src to dest. 
Argument dest must be a directory when src is a directory. 
Argument dest is assumed to be a file when src is a file. 
The src will be overwritten when dest = None.