Fixes #182: Updated logging to use slf4j and log4j

A few questions/thoughts:

1. There are a few places where the logger is initialized like so: 
```java
protected static final Logger LOG = LoggerFactory.getLogger("com.github.koraktor.steamcondenser");
```
They should probably all be pulled into one instance initialized in some sort of utility class or each should be initialized with their respective class

2. Do you want the logger to write to console? To a file instead? Something else?