Update README.md

Fixed minor typo.
Implement game world.
Merge remote-tracking branch 'origin/develop' into develop
Added new XML messages for movement.  Removed Messages.xml from client resources; they will have to be included in client binary, however.
Prototyped new ExecutableMessages
Removed "Known Issues" section of the README.md, since I've implemented string encryption over socket.
Changed database name and user info.  Updated tests and README.md to reflect this.
Made minor changes in the way classes are inherited to pave the way for easy-to-extend executable messages.
Added a few more messages and Executable Message prototypes.
Implemented ExecutableLoginRequest and necessary changes.
Finished implementing player login.
Added WorldSqlHandler class
Properly synchronized login.
Added IllegalArgumentException to World.addObject()
Fixed logger typo
Renamed ClientTest to ServerTest, as it more appropriately describes the tests being run.
Added login and logout functionality to WorldSQLHandler, including automatic saving of coordinates.  Closes #39.
Added ActorInfoClass, moved Vector2D and Round to jgcf.
Added ActorInvisibleMessage, ExecutableActorInvisibleMessage prototype.
Package restructuring