Fixed https://github.com/ronmamo/reflections/issues/11

Hi, I have fixed https://github.com/ronmamo/reflections/issues/11

The fix is more complex than just "return -1" as JarInputStream can also return entry with a size == -1 (which actually happened when I got sources and tried to run tests - VfsTest.jarInputStream() failed as it tried to read random class and JarInputStream was not able to calculate it's size)

The fix is to read entries into in-memory arrays.