Dockerfile for helping devs

[flaviostutz]

Provide a Dockerfile support to enable new incomers devs to develop without having to prepare his/hers local machine, causing incompatibilities with other dev's projects.

Proposal

Provide a Dockerfile and a docker-compose.yml file with an example on how to build/run Vegeta so that the specific tooling versions are very well defined.

Background

I am working on a new feature and decided to use successfuly Dockerfile in order to avoid having to prepare my host machine with libs/tools needed for building Vegeta.

Workarounds

Devs have to prepare his/hers machine with specific Make and Golang tools which may be incompatible with other projects the developer is working on too.

[Jmainguy]

PR for this appears to be open at https://github.com/tsenart/vegeta/pull/534

[tsenart]

Duplicate of #316