README maven logger should be runtime, not compile

[paulvi]

should be runtime, not compile dependencies.

[philsttr]

Thanks for the contribution @paulvi !

I agree that the example should use runtime by default, since the most common usage of logstash-logback-encoder is xml-configuration only.

However, logstash-logback-encoder provides many java extension points, for example:

• Custom Json Providers
• Appender Listeners
• Json Factory and Generator Decorators

If any of these extension points are used, then compile scope is needed.

Therefore, if the default example in the readme is changed to runtime scope, then a note needs to be added that describes A) when runtime scope can be used safely, and B) when compile scope must be used instead.

[paulvi]

Thanks,
README now has details