Switch from commons-logging to jcl-over-slf4j

Dropwizard 0.7.1 will include jcl-over-slf4j in dropwizard logging, which
clashes with jade4j and jets3t. Exclude the c-l dependency, pull in
jcl-over-slf4j at runtime.
Merge pull request #322 from hgschmie/commons-logging-fix

Switch from commons-logging to jcl-over-slf4j