Fix dependency convergence issues

**Issue**
Apps built with dropwizard-0.7.0-rc2 had two dependency convergence issues.  

1. Jackson 2.3.1 depends on jackson-annotations 2.3.0 which caused errors since dropwizard contains dependencies on jackson-annotations 2.3.1
2. Dropwizard depends on slf4j 1.7.6 but metrics imports slf4j 1.7.5

**Proposed Fix**

1. Switch jackson dependency back to 2.3.0
2. Exclude slf4j dependencies on all the metrics dependencies