improvements / fixes to vagrant rig (fixes #225)

- Properly bundles the static assets into the JAR now that they've moved to `SingularityService/target/generated-resources`
- Adds a `vagrantBuild` profile, which allows the JARs to be output somewhere else
- Prerequisites (zk, mysql, mesos) are now packaged into the vagrant box, which speeds up provisioning time considerably!
- Misc. cleanup / improvements to `provision-singularity.sh`

@hgschmie / @stevenschlansker: you guys are my Maven mavens -- do my custom profile and resource changes make sense?

/cc @StephanErb @seanedwards @Eseb @wsorenson