Customize logging

Instead of `NSLog`, `NBLog` will output a more developer friendly format. `NBLogLevel` and `NBLogging` provide a convention for classes (per implementation file) to have their own customizable logging level. Level-driven logging within the class can then be done through `NBLogDebug`, `NBLogInfo`, `NBLogWarning`, and `NBLogError` instead of `NBLog`. Default debug level is `NBLogLevelDebug`, and release level is `NBLogLevelWarning`.