Support for reading Unix FIFOs

[tobymiller]

Using readAsync on a Unix FIFO triggers the following exception:

java.io.IOException: Illegal seek
at java.base/sun.nio.ch.FileDispatcherImpl.pread0(Native Method)
at java.base/sun.nio.ch.FileDispatcherImpl.pread(FileDispatcherImpl.java:54)
at java.base/sun.nio.ch.IOUtil.readIntoNativeBuffer(IOUtil.java:274)
at java.base/sun.nio.ch.IOUtil.read(IOUtil.java:245)
at java.base/sun.nio.ch.IOUtil.read(IOUtil.java:223)
at java.base/sun.nio.ch.SimpleAsynchronousFileChannelImpl$2.run(SimpleAsynchronousFileChannelImpl.java:320)
at java.base/java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1429)
at java.base/java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:290)
at java.base/java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1016)
at java.base/java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1665)
at java.base/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1598)
at java.base/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:177)

It would be nice to be able to use this library with FIFOs, as they are particularly suited to use with observables.