Use generic version variable in dropwizard-example README
Use generic version variable in dropwizard-example README

Closes #2178

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dropwizard/dropwizard,jplock/dropwizard,phambryan/dropwizard,cvent/dropwizard,jplock/dropwizard,nickbabcock/dropwizard,cvent/dropwizard,dropwizard/dropwizard,jplock/dropwizard,cvent/dropwizard,micsta/dropwizard,pkwarren/dropwizard,patrox/dropwizard,phambryan/dropwizard,micsta/dropwizard,mosoft521/dropwizard,pkwarren/dropwizard,nickbabcock/dropwizard,pkwarren/dropwizard,micsta/dropwizard,patrox/dropwizard,patrox/dropwizard,nickbabcock/dropwizard,tjcutajar/dropwizard,Alexey1Gavrilov/dropwizard,tjcutajar/dropwizard,tjcutajar/dropwizard,phambryan/dropwizard,Alexey1Gavrilov/dropwizard,dropwizard/dropwizard,mosoft521/dropwizard,mosoft521/dropwizard,Alexey1Gavrilov/dropwizard