Issue #34: Improve error message when no committer configuration is available

[ivanramosnet]

Fix issue #34

You need to setup the git committer identity before using the action. The action fail if it does not find that configuration, at least for the commands that generate a commit. For example if you accidentally did not run

git config --global user.email "you@example.com"
or
git config --global user.name "Your Name"

before using the action.

If you use the action before running either of the config steps, you will see a message that looks something like this:

Git dir: "git dir path" has not been initialized

After applying this pull request you will see a message like this:

Git has not been setup:
  Run
  1. Run 'git config --global user.name <your name>
  2. Run 'git config --global user.email <your email>

[josecelano]

It seems we do not really need it.