Add the error code into the JSON response

Add the HTTP response code into the JSON error response
Merge pull request #666 from jplock/jp-json-error-codes

Add the error code into the JSON response
Merge remote-tracking branch 'upstream/master'
Fixes #678
Merge pull request #679 from mcarrierastonish/master

Fixes #678
Replace JaCoCo with Cobertura for code-coverage analysis

The JaCoCo Maven plugin currently doesn't support multi-module builds properly.
Cobertura doesn't completely work with Java 8 but at least it produces sensible
results for Dropwizard.
Avoid unnecessary (un-) boxing in Duration and Size (FindBugs)
Upgrade to FindBugs 3.0.0 (Java 8 compatible)
Fix client documentation
Merge pull request #684 from Toilal/docfix

Fix Liquibase example in dropwizard-migrations docs
Merge remote-tracking branch 'upstream/master'