Fix imports and pom.xml files
Interesting parts of conversion to Dropwizard 7
Conversion to codahale metrics from yammer
Rename banner.txt so Dropwizard 7 doesn't print it twice.

Now it gets printed manually in logBanner, which was always there.
This change just works around Dropwizard's auto-banner.txt printing.
Merge pull request #215 from spotify/drewc/dropwizard7

Conversion to Dropwizard 7 and Yammer->Codahale Metrics