Initial HDFS Readers and Writers implementation.

Basic implementation of a writer and sequential and random readers that operate with streams on HDFS. These operate on Array[Byte] rather than specific kinds of data, so any data being sent in should already be in serialized form.
But what happens when the file exists and append support isnt present? It will throw an error, right? And that may very well happen on some deployments. So any ways, all modules that use this have to any way be written such that filenames are unique, so that it does not fail on certain systems. Isnt it?

On that note, what happens if two WriteAheadLogWriters are simultaneous opened on the same file?