Fix reflection warnings

When running with *warn-on-reflection* true, I get the following warnings:

> Reflection warning, clj_logging_config/log4j.clj:201:47 - reference to field getScheme on java.lang.Object can't be resolved.
> Reflection warning, clj_logging_config/log4j.clj:202:75 - reference to field toURL on java.lang.Object can't be resolved.
> Reflection warning, clj_logging_config/log4j.clj:202:57 - reference to field getPath can't be resolved.
> Reflection warning, clj_logging_config/log4j.clj:205:47 - reference to field getScheme on java.lang.Object can't be resolved.
> Reflection warning, clj_logging_config/log4j.clj:206:57 - reference to field getPath on java.lang.Object can't be resolved.
> Reflection warning, clj_logging_config/log4j.clj:210:59 - call to java.io.FileWriter ctor can't be resolved.