Allow specifying target version

[arvindsv]

Equivalent of tomzo/gocd-json-config-plugin#12 for the yaml plugin.

Does this:

1. Updates README: Mostly Go => GoCD and *.go.cd to *.gocd.org.
2. Accept multiple patterns in the settings file. Old (single) patterns work too.
3. Allow specifying target version in the YAML.
4. Accept lock_behavior in the YAML.

It'll be like this, for every file:

format_version: 2
environments:
  env1: ...
  env2: ...
pipelines:
  pipe1:
      lock_behavior: "lockOnFailure"
      ...

[arvindsv]

@tomzo If you merge this, you can change the default format for #35.

As you know, you'll need to change it here and here to **/*.gocd.yaml, **/*.gocd.yml. If you want.

Oh, you'll also need to add a similar note about format_version in the README.

[arvindsv]

Just for the record, the corresponding PR in the GoCD codebase is gocd/gocd#3943.