fix:"ClassLoader.getSystemResourceAsStream" NullPointException

[gdjicasonjakesic]

Fix: #449

Problem
org.mp4parser.muxer.container.mp4.MovieCreator.build(path) throws NPE
Root cause
InputStream is = ClassLoader.getSystemResourceAsStream("isoparser2-default.properties");
returns null.
Fixed by replacing with

ClassLoader cs = Thread.currentThread().getContextClassLoader();
InputStream is = classLoader.getResourceAsStream("isoparser2-default.properties");