Replace client args parsing with JCommander

Command argument parsing is lame.
Implement client-specified consistency level

Semantics and names from Cassandra.
Clarify "files" section of README

fix spelling mistakes, reduce verbosity.
Implement `offset` list parameter

Also limit listing to 10 articles max.
Implement read-your-write consistency

i.e. local persistent writes for the client.

The coordinator requirement makes it less convenient, but
at least it works.
Document jcommander and ArticleStore
Balance load in coordinator broadcasts

i.e. shuffle nodes before broadcasting reads/writes
Implement `sync` background task

Stupid, non-scalable implementation, but that's okay,
cause it works.
Merge branch 'master' into consistency

Conflicts:
	Server/MasterServer.java
	Server/Node.java
	testClientMethods.java
Shutdown test runner at end of main()

Something with the processes is hanging the vm
after the main thread ends...
Add test runner script

With classpath set