producer republish command

[mcarmonaa]

Added a new subcommand republish to the producer command to republish buried jobs:

Usage:
  borges [OPTIONS] producer republish [republish-OPTIONS]

Help Options:
  -h, --help               Show this help message

[republish command options]
          --queue=         queue name (default: borges)
          --loglevel=      max log level enabled (default: info)
          --logfile=       path to file where logs will be stored
          --metrics        expose a metrics endpoint using an HTTP server
          --metrics-port=  port to bind metrics to (default: 6062)
          --profiler       start CPU, memory and block profilers
          --profiler-port= port to bind profiler to (default: 6061)
          --priority=      priority used to enqueue jobs, goes from 0 (lowest) to :MAX: (highest)
                           (default: 4)
          --job-retries=   number of times a falied job should be processed again before reject it
                           (default: 5)
      -t, --time=          elapsed time between republish triggers (default: 0)

It depends on src-d/framework#40 and #251.

Closes #242

[erizocosmico]

LGTM when travis passes