added NMEAFile.parse() function which can be overriden to match particular file formats (default calls NMEASentence.parse on the line)
added NMEAFile.parse() function which can be overriden to match particular file formats (default calls NMEASentence.parse on the line)

silentquasar/pynmea2,lobocv/pynmea2,Knio/pynmea2