Takes data frame or vector of chromosome position ranges and parses to granges object
     
    
    Usage
    parse_chrompos(chrompos, radius = NULL)
 
     
    
    Arguments
- chrompos
 
Either vector of chromosome and position ranges e.g. "1:1000" or "1:1000-2000", or data frame with columns chrom, start, end.
 
- radius
 
Add radius to the specified positions. Default = NULL