style: Improve logging associated with release, assets and references

[jcfr]

Here are few examples of output:

$ githubrelease release jcfr/sandbox list

release 'nightly' info
  Tag name      : nightly
  Name          : nightly (updated on 20170212)
  ID            : 5427736
  Created       : 2017-02-01T07:31:19Z
  URL           : https://github.com/jcfr/sandbox/releases/tag/nightly
  Author        : jcfr
  Is published  : True
  Is prerelease : True

  Asset #0
    name      : sandbox-4.12.0.dev20170212-cp27-cp27m-win32.whl
    size      : 52
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp27-cp27m-win32.whl
    Downloads : 0

  Asset #1
    name      : sandbox-4.12.0.dev20170212-cp27-cp27m-win_amd64.whl
    size      : 56
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp27-cp27m-win_amd64.whl
    Downloads : 0

  Asset #2
    name      : sandbox-4.12.0.dev20170212-cp34-cp34m-win32.whl
    size      : 52
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp34-cp34m-win32.whl
    Downloads : 0

  Asset #3
    name      : sandbox-4.12.0.dev20170212-cp34-cp34m-win_amd64.whl
    size      : 56
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp34-cp34m-win_amd64.whl
    Downloads : 0

  Asset #4
    name      : sandbox-4.12.0.dev20170212-cp35-cp35m-win32.whl
    size      : 52
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp35-cp35m-win32.whl
    Downloads : 0

  Asset #5
    name      : sandbox-4.12.0.dev20170212-cp35-cp35m-win_amd64.whl
    size      : 56
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp35-cp35m-win_amd64.whl
    Downloads : 0

  Asset #6
    name      : sandbox-4.12.0.dev20170212-cp36-cp36m-win32.whl
    size      : 52
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp36-cp36m-win32.whl
    Downloads : 0

  Asset #7
    name      : sandbox-4.12.0.dev20170212-cp36-cp36m-win_amd64.whl
    size      : 56
    uploader  : jcfr
    URL       : https://github.com/jcfr/sandbox/releases/download/nightly/sandbox-4.12.0.dev20170212-cp36-cp36m-win_amd64.whl
    Downloads : 0

$ githubrelease ref jcfr/sandbox list --verbose
Reference 'refs/heads/master'
  Object
    type : commit
    sha  : 0616014562f225a86469fffe39219536a53b56b1

Reference 'refs/tags/nightly'
  Object
    type : commit
    sha  : 0616014562f225a86469fffe39219536a53b56b1

$ githubrelease release jcfr/sandbox create my-tag
created 'my-tag' release
  Tag name      : my-tag
  ID            : 5427757
  Created       : 2017-02-11T06:23:39Z
  URL           : https://github.com/jcfr/sandbox/releases/tag/untagged-cfccf5564b71b4d4a2a0
  Author        : jcfr
  Is published  : False
  Is prerelease : False